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Polynomial long and synthetic division

Learning goals

  • Divides polynomials using long division.
  • Uses synthetic division when its conditions are met.
  • Interprets quotient and remainder correctly.
  • Checks the result by multiplication and addition of the remainder.

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Polynomial long and synthetic division 1
You are setting up synthetic division for \(P(x)=x^3-5x+2\) divided by \(x-4\). What number goes outside the synthetic-division box, and what coefficient row should be written inside? Do not carry out the division.

Hints

- Compare the divisor with the standard form \(x-c\). - List coefficients in descending powers of \(x\). - Check whether any power is missing and needs a placeholder coefficient.

Solution

1. Synthetic division by \(x-c\) uses the number \(c\). Since the divisor is \(x-4\), the outside number is \(4\). 2. The polynomial has no \(x^2\) term, so its coefficient must be recorded as \(0\). 3. The coefficient row is \(1, 0, -5, 2\).

Answer

Outside number: \(4\) Coefficient row: \(1, 0, -5, 2\)
Polynomial long and synthetic division 2
Start polynomial long division of \(6x^2+5x+1\) by \(2x+1\). What is the first term of the quotient? Explain how you found it.

Hints

- Which term has the highest power in the dividend and in the divisor? - Find a term that would cancel the dividend's highest-power term when multiplied by the divisor.

Solution

1. Divide the leading terms: \(\frac{6x^2}{2x}=3x\). 2. Write \(3x\) as the first quotient term. Multiplying \(3x(2x+1)\) will cancel the leading \(6x^2\) term in the dividend.

Answer

\(3x\), because \(6x^2\div 2x=3x\).
Polynomial long and synthetic division 3
A polynomial is written as \(P(x)=(x-3)(x^2+2)+5\). When \(P(x)\) is divided by \(x-3\), what are the quotient and remainder?

Hints

- Which part is multiplied by the divisor? - What part is left over after that product?

Solution

1. Compare the given expression with \(P(x)=d(x)Q(x)+R\). 2. The factor multiplying \(x-3\) is the quotient \(x^2+2\). 3. The number added afterward is the remainder \(5\).

Answer

Quotient: \(x^2+2\); remainder: \(5\).
Polynomial long and synthetic division 4
To divide a polynomial by \(x+4\) using synthetic division, which number goes outside the synthetic-division row? Explain the sign.

Hints

- What value of \(x\) makes the divisor equal zero? - Compare the divisor with the form \(x-c\).

Solution

1. Write the divisor as \(x-(-4)\). 2. Synthetic division uses the number that makes the divisor zero, so the number is \(-4\).

Answer

\(-4\), because \(x+4=0\) when \(x=-4\).
Polynomial long and synthetic division 5
Write the coefficient row needed for synthetic division of \(4x^4-2x+7\). Include zeros for any missing powers.

Hints

- Which powers lie between the highest power and the linear term? - How do you record a power that is not written in the expression?

Solution

1. List the powers from \(x^4\) down to \(x^0\). 2. The coefficients of \(x^3\) and \(x^2\) are both \(0\). 3. The coefficient row is \(4,\ 0,\ 0,\ -2,\ 7\).

Answer

\(4,\ 0,\ 0,\ -2,\ 7\)
Polynomial long and synthetic division 6
A polynomial is divided by \(x^2+1\). Which expression could be its remainder: \(3x-2\) or \(x^2+4\)? Explain.

Hints

- How does the degree of the remainder compare with the divisor's degree? - Which choice contains a squared term?

Solution

1. The divisor has degree \(2\). 2. A remainder must have degree less than \(2\), unless it is zero. 3. The linear expression \(3x-2\) is possible, but \(x^2+4\) has degree \(2\) and cannot be the final remainder.

Answer

\(3x-2\), because the remainder must have degree less than \(2\).
Polynomial long and synthetic division 7
Use synthetic division to divide \(x^3+2x^2-5x-6\) by \(x+1\). State the quotient and remainder.

Hints

- Rewrite the divisor mentally in the form \(x-c\) to identify the synthetic value. - Use the coefficients in descending-power order. - The final synthetic entry is the remainder.

Solution

1. For divisor \(x+1=x-(-1)\), use synthetic value \(-1\) with coefficients \(1,2,-5,-6\). 2. Bring down \(1\); multiply by \(-1\) and add to get \(1\); multiply by \(-1\) and add to get \(-6\); multiply by \(-1\) and add to get remainder \(0\). 3. The quotient is \(x^2+x-6\) and the remainder is \(0\).

Answer

Quotient: \(x^2+x-6\); remainder: \(0\)
Polynomial long and synthetic division 8
Use synthetic division to divide \(2x^4-3x^2+5x-4\) by \(x-1\). State the quotient and remainder.

Hints

- Write a zero coefficient for every missing power before starting synthetic division. - Use the constant from \(x-1\) as the synthetic value. - Match the quotient coefficients to descending powers one degree lower than the dividend.

Solution

1. The polynomial has no \(x^3\)-term, so use coefficients \(2,0,-3,5,-4\) with synthetic value \(1\). 2. Bring down \(2\); multiply by \(1\) and add to get \(2\); multiply by \(1\) and add to get \(-1\); multiply by \(1\) and add to get \(4\); multiply by \(1\) and add to get remainder \(0\). 3. The quotient is \(2x^3+2x^2-x+4\).

Answer

Quotient: \(2x^3+2x^2-x+4\); remainder: \(0\)
Polynomial long and synthetic division 9
Use synthetic division to divide \(x^3-4x+7\) by \(x-2\). Write the result in the form \(\text{dividend}=(\text{divisor})(\text{quotient})+\text{remainder}\).

Hints

- Include a zero coefficient for the missing \(x^2\)-term. - A nonzero final synthetic entry is the remainder, not another quotient coefficient. - Use the division identity to write the result after completing the synthetic work.

Solution

1. Include the missing \(x^2\)-term and use coefficients \(1,0,-4,7\) with synthetic value \(2\). 2. Bring down \(1\); multiply by \(2\) and add to get \(2\); multiply by \(2\) and add to get \(0\); multiply by \(2\) and add to get remainder \(7\). 3. The quotient is \(x^2+2x\), so \(x^3-4x+7=(x-2)(x^2+2x)+7\).

Answer

Quotient: \(x^2+2x\); remainder: \(7\) \(x^3-4x+7=(x-2)(x^2+2x)+7\)
Polynomial long and synthetic division 10
Use polynomial long division to divide \(2x^3+3x^2-8x-12\) by \(x+2\). State the quotient and remainder.

Hints

- At each stage, divide the current leading term by the divisor's leading term. - Multiply the entire divisor by the new quotient term before subtracting. - Continue until the remaining degree is less than the divisor's degree.

Solution

1. Divide the leading terms: \(2x^3\div x=2x^2\). Multiply \(x+2\) by \(2x^2\) and subtract, leaving \(-x^2-8x-12\). 2. Divide \(-x^2\div x=-x\). Multiply \(x+2\) by \(-x\) and subtract, leaving \(-6x-12\). 3. Divide \(-6x\div x=-6\). Multiply \(x+2\) by \(-6\) and subtract, leaving remainder \(0\). 4. The quotient is \(2x^2-x-6\).

Answer

Quotient: \(2x^2-x-6\); remainder: \(0\)
Polynomial long and synthetic division 11
For each division, choose the more appropriate method from synthetic division or polynomial long division. Explain why the other method is not the natural choice. a) \((x^3-5x+2)\div(x-3)\) b) \((2x^4+x^2-1)\div(x^2+1)\)

Hints

- Look first at the degree and form of each divisor. - Which divisors can be represented by one synthetic value? - Compare the method requirements before choosing.

Solution

1. In part a, the divisor \(x-3\) is linear and has the form \(x-c\). Synthetic division is more efficient, although long division would also work. 2. In part b, the divisor \(x^2+1\) has degree \(2\). Polynomial long division is appropriate because standard synthetic division in this course is used for divisors of the form \(x-c\).

Answer

a) Synthetic division, because the divisor is of the form \(x-c\). Long division also works but takes more steps. b) Polynomial long division, because the divisor is quadratic. Standard synthetic division applies to divisors of the form \(x-c\).
Polynomial long and synthetic division 12
A division calculation claims that dividing \(x^3-x^2+2x-3\) by \(x-2\) gives quotient \(x^2+x+4\) and remainder \(5\). Verify the claim using the identity \(\text{dividend}=(\text{divisor})(\text{quotient})+\text{remainder}\).

Hints

- Verification reverses polynomial division. - Multiply the divisor by the proposed quotient first. - Add the proposed remainder only after expanding the product.

Solution

1. Multiply the divisor and quotient: \((x-2)(x^2+x+4)=x^3-x^2+2x-8\). 2. Add the claimed remainder: \(x^3-x^2+2x-8+5=x^3-x^2+2x-3\). 3. This matches the dividend exactly, so the quotient and remainder are correct.

Answer

The claim is correct because \((x-2)(x^2+x+4)+5=x^3-x^2+2x-3\).
Polynomial long and synthetic division 13
Use polynomial long division to divide \(6x^3+5x^2-16x-6\) by \(2x+3\). State the quotient and remainder, then verify your result with the polynomial division identity.

Hints

- In long division, divide the current leading term by the divisor's leading term at each stage. - After each quotient term, multiply the entire divisor and subtract. - At the end, check that the remainder has lower degree than the divisor and reconstruct the dividend.

Solution

1. Divide the leading terms: \(6x^3\div 2x=3x^2\). Multiply back and subtract to obtain \(-4x^2-16x\). 2. Divide again: \(-4x^2\div 2x=-2x\). Multiply back and subtract to obtain \(-10x-6\). 3. Divide once more: \(-10x\div 2x=-5\). Multiply back and subtract to obtain the remainder \(9\). 4. The quotient is \(3x^2-2x-5\), with remainder \(9\). 5. Verification: \((2x+3)(3x^2-2x-5)+9=6x^3+5x^2-16x-6\), which reproduces the dividend.

Answer

Quotient: \(3x^2-2x-5\) Remainder: \(9\)
Polynomial long and synthetic division 14
Divide \(x^2+4x+8\) by \(x+2\) using polynomial long division. Give the quotient and remainder.

Hints

- What should multiply the divisor to cancel the highest power first? - After subtracting, repeat the same step with the term of highest degree that remains. - When does the division process stop?

Solution

1. Divide \(x^2\) by \(x\) to get the first quotient term \(x\). 2. Subtract \(x(x+2)=x^2+2x\) to leave \(2x+8\). 3. Divide \(2x\) by \(x\) to get \(2\); subtract \(2(x+2)=2x+4\). 4. The remainder is \(4\), so the quotient is \(x+2\).

Answer

Quotient: \(x+2\); remainder: \(4\).
Polynomial long and synthetic division 15
Complete the synthetic division of \(2x^3-3x^2+5\) by \(x-2\). After bringing down the first coefficient, the bottom row starts with \(2\). Find the next three numbers in that row.

Hints

- Which missing-power coefficient should appear before the constant? - In synthetic division, what happens to each new bottom-row entry before you add in the next column? - The final entry represents the remainder.

Solution

1. Use the coefficient row \(2,-3,0,5\), including the missing \(x\)-term. 2. Multiply the first bottom-row entry \(2\) by \(2\) and add to \(-3\), giving \(1\). 3. Multiply \(1\) by \(2\) and add to \(0\), giving \(2\). 4. Multiply \(2\) by \(2\) and add to \(5\), giving \(9\).

Answer

The next three entries are \(1,\ 2,\ 9\).
Polynomial long and synthetic division 16
A student divides \(P(x)=x^3+x+3\) by \(x-1\) and reports quotient \(Q(x)=x^2+x+2\) and remainder \(5\). Check the result by multiplication, without redoing the division.

Hints

- What equation must connect a dividend, divisor, quotient, and remainder? - Multiply the proposed quotient by the divisor first. - Does adding the remainder reproduce the original polynomial?

Solution

1. A correct division must satisfy \(P(x)=(x-1)Q(x)+5\). 2. Multiply: \((x-1)(x^2+x+2)=x^3+x-2\). 3. Add \(5\) to get \(x^3+x+3=P(x)\). The proposed division is correct.

Answer

Correct: \((x-1)(x^2+x+2)+5=x^3+x+3\).
Polynomial long and synthetic division 17
A student wants to divide \(P(x)=x^4-16\) by \(x^2-4\). They suggest using synthetic division with \(2\), saying this is the same as dividing by \(x^2-4\). Is that correct? Explain what synthetic division with \(2\) actually divides by.

Hints

- What is the actual divisor when the number in synthetic division is \(2\)? - Compare the degrees of that divisor and the one in the question. - Would using only one factor of a product be equivalent to dividing by the whole product?

Solution

1. Synthetic division with \(2\) divides by the linear expression \(x-2\). 2. The requested divisor \(x^2-4=(x-2)(x+2)\) has two linear factors, so one synthetic division by \(x-2\) is not the complete requested division. 3. The student's claim is false. Long division by \(x^2-4\) would divide by the whole quadratic divisor.

Answer

No. Synthetic division with \(2\) divides by \(x-2\), not by \(x^2-4\).
Polynomial long and synthetic division 18
The polynomial function \(f\) is defined by \(f(x)=x^3-2x^2-13x-10\). 1. Use synthetic division and the fact that \(x=-1\) is a zero to reduce \(f\) to a quadratic, then find all zeros of \(f\). 2. Write \(f(x)\) in factored form as a product of linear factors. 3. State the multiplicity of each zero.

Hints

- A known zero \(x=a\) gives a factor \(x-a\) and a synthetic value \(a\). - Keep the polynomial coefficients in descending-power order during synthetic division. - Factor the quadratic quotient after the division is complete. - In complete factored form, the exponent on each factor gives the multiplicity.

Solution

1. Since \(x=-1\) is a zero, divide by \(x+1\) using synthetic value \(-1\). Use coefficients \(1,-2,-13,-10\): bring down \(1\); multiply by \(-1\) and add to get \(-3\); multiply by \(-1\) and add to get \(-10\); multiply by \(-1\) and add to get remainder \(0\). The quotient is \(x^2-3x-10\). Factor the quotient: \(x^2-3x-10=(x-5)(x+2)\). Therefore, the zeros are \(x=-2\), \(x=-1\), and \(x=5\). 2. The factored form is \(f(x)=(x+1)(x-5)(x+2)\). 3. Each linear factor occurs once, so each zero has multiplicity \(1\).

Answer

1. \(x=-2\), \(x=-1\), and \(x=5\) 2. \(f(x)=(x+1)(x-5)(x+2)\) 3. Each zero has multiplicity \(1\).
Polynomial long and synthetic division 19
The polynomial function \(f\) is defined by \(f(x)=x^3-6x^2+3x+10\). Given that \(x=-1\) is a zero, use synthetic division to find all remaining zeros.

Hints

- A known zero identifies the synthetic value and corresponding linear factor. - Keep the coefficients in descending-power order. - A zero remainder confirms that the known zero's factor divided evenly. - Factor the quadratic quotient to find the remaining zeros.

Solution

1. The zero \(x=-1\) corresponds to the factor \(x+1\), so use synthetic value \(-1\) with coefficients \(1,-6,3,10\). 2. Bring down \(1\). Multiply by \(-1\) and add to get \(-7\). Multiply by \(-1\) and add to get \(10\). Multiply by \(-1\) and add to get remainder \(0\). The quotient is \(x^2-7x+10\). 3. Factor the quotient: \(x^2-7x+10=(x-2)(x-5)\). 4. Therefore, the remaining zeros are \(x=2\) and \(x=5\).

Answer

\(x=2\) and \(x=5\)
Polynomial long and synthetic division 20
Factor \(p(x)=2x^3-4x^2-22x+24\) completely into linear factors. First verify whether \(x=1\) is a zero, and then use synthetic division by the corresponding linear factor.

Hints

- Substituting a value that produces \(0\) confirms a zero and its corresponding linear factor. - Use the confirmed zero as the synthetic value. - Keep track of the leading coefficient when factoring the quadratic quotient. - Check that the final product has the same degree and leading coefficient as the original polynomial.

Solution

1. Evaluate the polynomial: \(p(1)=2-4-22+24=0\). Therefore, \(x=1\) is a zero and \(x-1\) is a factor. 2. Use synthetic value \(1\) with coefficients \(2,-4,-22,24\). Bring down \(2\); multiply by \(1\) and add to get \(-2\); multiply by \(1\) and add to get \(-24\); multiply by \(1\) and add to get remainder \(0\). The quotient is \(2x^2-2x-24\). 3. Factor the quotient: \(2x^2-2x-24=2(x^2-x-12)=2(x-4)(x+3)\). 4. Therefore, the complete factorization is \(p(x)=2(x-1)(x-4)(x+3)\).

Answer

\(p(x)=2(x-1)(x-4)(x+3)\)
Polynomial long and synthetic division 21
The polynomial function \(f\) is defined by \(f(x)=x^3-6x^2-x+30\), and \(x=3\) is a known zero. a) Explain how the known zero identifies the synthetic-division value and the corresponding linear factor. b) Use synthetic division to find all remaining zeros and write \(f(x)\) as a product of linear factors.

Hints

- A known zero determines both the divisor factor and its synthetic-division value. - Keep coefficients in descending-power order during synthetic division. - Use the remainder to check the factor before finding the other zeros. - Factor the quadratic quotient to find the remaining zeros.

Solution

1. Since \(x=3\) is a zero, \(x-3\) is a factor and the synthetic-division value is \(3\). 2. Use coefficients \(1,-6,-1,30\). Bring down \(1\), then multiply by \(3\) and add successively to obtain \(-3\), \(-10\), and remainder \(0\). The quotient is \(x^2-3x-10\). 3. Factor the quotient: \(x^2-3x-10=(x-5)(x+2)\). The remaining zeros are \(5\) and \(-2\), and \(f(x)=(x-3)(x-5)(x+2)\).

Answer

a) Since \(f(3)=0\), \(x-3\) is a factor and the synthetic-division value is \(3\). b) Remaining zeros: \(x=-2\) and \(x=5\); \(f(x)=(x-3)(x-5)(x+2)\)
Polynomial long and synthetic division 22
The polynomial function \(f\) is defined by \(f(x)=x^3-4x^2+x+6\). First test \(x=\pm1\) and \(x=\pm2\) by substitution to determine which are zeros. Then use synthetic division with one confirmed zero to find all remaining zeros of \(f\).

Hints

- Substitute each proposed value and check whether the output is \(0\). - Use one confirmed zero as the synthetic value to reduce the cubic to a quadratic. - Keep the coefficients in descending-power order. - Factor the quadratic quotient to finish finding the zeros.

Solution

1. Evaluate the proposed values: \(f(1)=4\), \(f(-1)=0\), \(f(2)=0\), and \(f(-2)=-20\). Therefore, \(x=-1\) and \(x=2\) are zeros among the tested values. 2. Use synthetic value \(-1\) with coefficients \(1,-4,1,6\). Bring down \(1\); multiply by \(-1\) and add to get \(-5\); multiply by \(-1\) and add to get \(6\); multiply by \(-1\) and add to get remainder \(0\). The quotient is \(x^2-5x+6\). 3. Factor the quotient: \(x^2-5x+6=(x-2)(x-3)\). 4. Thus, all zeros are \(x=-1\), \(x=2\), and \(x=3\).

Answer

Tested zeros: \(x=-1\) and \(x=2\) All zeros: \(x=-1\), \(x=2\), and \(x=3\)
Polynomial long and synthetic division 23
The fourth-degree polynomial function \(h\) is defined by \(h(x)=x^4-4x^3-7x^2+22x+24\). Two zeros are known: \(x=-2\) and \(x=3\). Use repeated synthetic division to find the remaining zeros.

Hints

- Use each known zero as a synthetic value, one after the other. - Keep the quotient coefficients in descending-power order before the second division. - A zero remainder at each stage confirms that the corresponding linear factor divides evenly. - Factor the final quadratic quotient.

Solution

1. Use synthetic value \(-2\) with coefficients \(1,-4,-7,22,24\). Bring down \(1\); multiply by \(-2\) and add to get \(-6\); multiply by \(-2\) and add to get \(5\); multiply by \(-2\) and add to get \(12\); multiply by \(-2\) and add to get remainder \(0\). The quotient is \(x^3-6x^2+5x+12\). 2. Use synthetic value \(3\) with quotient coefficients \(1,-6,5,12\). Bring down \(1\); multiply by \(3\) and add to get \(-3\); multiply by \(3\) and add to get \(-4\); multiply by \(3\) and add to get remainder \(0\). The new quotient is \(x^2-3x-4\). 3. Factor the quadratic: \(x^2-3x-4=(x-4)(x+1)\). 4. Therefore, the remaining zeros are \(x=4\) and \(x=-1\).

Answer

\(x=-1\) and \(x=4\)
Polynomial long and synthetic division 24
Consider \(p(x)=x^4+2x^3-7x^2-8x+12\). The values \(x=1\) and \(x=-2\) are known zeros. Use repeated synthetic division to factor \(p(x)\) completely into linear factors and find all zeros.

Hints

- Use each known zero as a synthetic value, one at a time. - Each zero remainder lowers the degree by \(1\) and confirms the corresponding linear factor. - Factor the remaining quadratic after the two divisions. - Check the signs in the factors: a zero \(r\) corresponds to \(x-r\).

Solution

1. Use synthetic value \(1\) with coefficients \(1,2,-7,-8,12\). Bring down \(1\); multiply by \(1\) and add to get \(3\); multiply by \(1\) and add to get \(-4\); multiply by \(1\) and add to get \(-12\); multiply by \(1\) and add to get remainder \(0\). The quotient is \(x^3+3x^2-4x-12\). 2. Use synthetic value \(-2\) with coefficients \(1,3,-4,-12\). Bring down \(1\); multiply by \(-2\) and add to get \(1\); multiply by \(-2\) and add to get \(-6\); multiply by \(-2\) and add to get remainder \(0\). The quotient is \(x^2+x-6\). 3. Factor the remaining quadratic: \(x^2+x-6=(x-2)(x+3)\). 4. Therefore, \(p(x)=(x-1)(x+2)(x-2)(x+3)\). The zeros are \(x=-3\), \(x=-2\), \(x=1\), and \(x=2\).

Answer

The complete factorization is \(p(x)=(x-1)(x+2)(x-2)(x+3)\). The zeros are \(x=-3\), \(x=-2\), \(x=1\), and \(x=2\).
Polynomial long and synthetic division 25
The polynomial function is \(f(x)=x^4-4x^3+3x^2+4x-4\). Determine the multiplicity of the zero \(x=2\) by repeatedly using synthetic division with the factor \(x-2\). Then give the complete factorization of \(f(x)\).

Hints

- Use the zero \(2\) as the synthetic value each time you test another copy of the factor \(x-2\). - Count consecutive zero remainders to determine multiplicity. - When a quotient no longer gives zero at \(x=2\), stop dividing by \(x-2\). - Factor the final quotient completely.

Solution

1. Verify the zero: \(f(2)=16-32+12+8-4=0\). 2. Use synthetic value \(2\) with coefficients \(1,-4,3,4,-4\). Bring down \(1\); multiply by \(2\) and add to get \(-2\); multiply by \(2\) and add to get \(-1\); multiply by \(2\) and add to get \(2\); multiply by \(2\) and add to get remainder \(0\). The quotient is \(x^3-2x^2-x+2\). 3. Divide again using synthetic value \(2\) with coefficients \(1,-2,-1,2\). Bring down \(1\); multiply by \(2\) and add to get \(0\); multiply by \(2\) and add to get \(-1\); multiply by \(2\) and add to get remainder \(0\). The quotient is \(x^2-1\). 4. The remaining quotient is not divisible by \(x-2\) because \(2^2-1=3\ne0\). Therefore, \(x=2\) has multiplicity \(2\). 5. Factor \(x^2-1=(x-1)(x+1)\). Thus, \(f(x)=(x-2)^2(x-1)(x+1)\).

Answer

The zero \(x=2\) has multiplicity \(2\). The complete factorization is \(f(x)=(x-2)^2(x-1)(x+1)\).
Polynomial long and synthetic division 26
The function is \(h(x)=x^4-3x^3-6x^2+28x-24\). Show that \(x=2\) is a zero of multiplicity \(3\) by using synthetic division with \(x-2\) three times. Find the remaining factor \(g(x)\), and use it to explain why \(x=2\) does not have multiplicity \(4\).

Hints

- Use \(2\) as the synthetic value for each successive division. - Each zero remainder confirms one more copy of the factor \(x-2\). - After the third successful division, test the remaining factor at \(x=2\).

Solution

1. Use synthetic value \(2\) with coefficients \(1,-3,-6,28,-24\). Bring down \(1\); multiply by \(2\) and add to get \(-1\); multiply by \(2\) and add to get \(-8\); multiply by \(2\) and add to get \(12\); multiply by \(2\) and add to get remainder \(0\). The quotient is \(x^3-x^2-8x+12\). 2. Divide again with coefficients \(1,-1,-8,12\). Bring down \(1\); multiply by \(2\) and add to get \(1\); multiply by \(2\) and add to get \(-6\); multiply by \(2\) and add to get remainder \(0\). The quotient is \(x^2+x-6\). 3. Divide a third time with coefficients \(1,1,-6\). Bring down \(1\); multiply by \(2\) and add to get \(3\); multiply by \(2\) and add to get remainder \(0\). The remaining factor is \(g(x)=x+3\). 4. Since \(g(2)=5\ne0\), a fourth division by \(x-2\) would not have zero remainder. Therefore, \(x=2\) has multiplicity \(3\), not \(4\).

Answer

After three divisions, \(g(x)=x+3\). Because \(g(2)=5\ne0\), \(x=2\) has multiplicity \(3\) and not multiplicity \(4\).
Polynomial long and synthetic division 27
Find all zeros of \(f(x)=x^4+x^3-7x^2-5x+10\). First test integer factors of the constant term, and then use repeated synthetic division to reduce the degree.

Hints

- Possible integer zeros are related to factors of the constant term. - Once an integer zero is confirmed, use it as a synthetic value to lower the degree. - Repeat the process with another confirmed zero. - Solve the final quadratic equation exactly.

Solution

1. The possible integer zeros are among \(\pm1\), \(\pm2\), \(\pm5\), and \(\pm10\). Testing shows that \(f(1)=0\) and \(f(-2)=0\). 2. Use synthetic value \(1\) with coefficients \(1,1,-7,-5,10\). Bring down \(1\); multiply by \(1\) and add to get \(2\); multiply by \(1\) and add to get \(-5\); multiply by \(1\) and add to get \(-10\); multiply by \(1\) and add to get remainder \(0\). The quotient is \(x^3+2x^2-5x-10\). 3. Use synthetic value \(-2\) with coefficients \(1,2,-5,-10\). Bring down \(1\); multiply by \(-2\) and add to get \(0\); multiply by \(-2\) and add to get \(-5\); multiply by \(-2\) and add to get remainder \(0\). The quotient is \(x^2-5\). 4. Solve \(x^2-5=0\): \(x=-\sqrt{5}\) or \(x=\sqrt{5}\). 5. Therefore, the zeros are \(x=-\sqrt{5}\), \(x=-2\), \(x=1\), and \(x=\sqrt{5}\).

Answer

The zeros are \(x=-\sqrt{5}\), \(x=-2\), \(x=1\), and \(x=\sqrt{5}\).
Polynomial long and synthetic division 28
Find all zeros of \(f(x)=x^5-2x^4-4x^3+8x^2+3x-6\). Test possible integer zeros and use synthetic division repeatedly until a quadratic equation remains.

Hints

- Start by testing integer factors of the constant term. - Use each confirmed zero as a synthetic value. - After each zero remainder, continue with the quotient coefficients. - Stop when the quotient is quadratic, then solve that equation exactly.

Solution

1. Possible integer zeros are among \(\pm1\), \(\pm2\), \(\pm3\), and \(\pm6\). Testing identifies \(x=1\), \(x=-1\), and \(x=2\) as zeros. 2. Use synthetic value \(1\) with coefficients \(1,-2,-4,8,3,-6\). Bring down \(1\); multiply and add successively to obtain \(-1,-5,3,6\), then remainder \(0\). The quotient is \(x^4-x^3-5x^2+3x+6\). 3. Use synthetic value \(-1\) with coefficients \(1,-1,-5,3,6\). Bring down \(1\); multiply and add successively to obtain \(-2,-3,6\), then remainder \(0\). The quotient is \(x^3-2x^2-3x+6\). 4. Use synthetic value \(2\) with coefficients \(1,-2,-3,6\). Bring down \(1\); multiply and add successively to obtain \(0,-3\), then remainder \(0\). The quotient is \(x^2-3\). 5. Solve \(x^2-3=0\): \(x=-\sqrt{3}\) or \(x=\sqrt{3}\). 6. Therefore, the zeros are \(x=-\sqrt{3}\), \(x=-1\), \(x=1\), \(x=\sqrt{3}\), and \(x=2\).

Answer

The zeros are \(x=-\sqrt{3}\), \(x=-1\), \(x=1\), \(x=\sqrt{3}\), and \(x=2\).
Polynomial long and synthetic division 29
Find the coordinates of all intersection points of \(f(x)=-x^3+3x^2\) and \(g(x)=4\) algebraically. After finding one integer solution of the resulting cubic equation, use synthetic division to reduce the cubic.

Hints

- Set the two polynomial expressions equal and move all terms to one side. - After finding an integer solution, use it as the synthetic value. - Remember to include a zero coefficient for any missing power in the cubic. - Factor the quadratic quotient and then use either original function for the y-coordinates.

Solution

1. Set the functions equal: \(-x^3+3x^2=4\), so \(x^3-3x^2+4=0\). 2. Test small integer values. Since \((-1)^3-3(-1)^2+4=0\), \(x=-1\) is a solution and \(x+1\) is a factor. 3. The cubic has coefficients \(1,-3,0,4\); include the zero coefficient for the missing \(x\)-term. Use synthetic value \(-1\): bring down \(1\); multiply by \(-1\) and add to get \(-4\); multiply by \(-1\) and add to get \(4\); multiply by \(-1\) and add to get remainder \(0\). The quotient is \(x^2-4x+4\). 4. Factor the quotient: \(x^2-4x+4=(x-2)^2\). Therefore, the x-coordinates are \(x=-1\) and \(x=2\). 5. Because \(g(x)=4\), both corresponding y-coordinates are \(4\). 6. The intersection points are \((-1, 4)\) and \((2, 4)\).

Answer

The intersection points are \((-1, 4)\) and \((2, 4)\).
Polynomial long and synthetic division 30
Use polynomial long division to divide \(2x^4+x^3-8x^2-x+6\) by \(x^2+x-2\). State the quotient and remainder.

Hints

- Synthetic division is not appropriate for a quadratic divisor, so use long division. - Divide leading terms to determine each new quotient term. - Subtract the full product at every stage and keep like powers aligned.

Solution

1. Divide \(2x^4\) by \(x^2\) to get \(2x^2\). Multiply the divisor by \(2x^2\) and subtract, leaving \(-x^3-4x^2-x+6\). 2. Divide \(-x^3\) by \(x^2\) to get \(-x\). Multiply the divisor by \(-x\) and subtract, leaving \(-3x^2-3x+6\). 3. Divide \(-3x^2\) by \(x^2\) to get \(-3\). Multiply the divisor by \(-3\) and subtract, leaving remainder \(0\). 4. The quotient is \(2x^2-x-3\).

Answer

Quotient: \(2x^2-x-3\); remainder: \(0\)
Polynomial long and synthetic division 31
Use polynomial long division to divide \(x^4+2x^2-3\) by \(x^2-x+1\). State the quotient and remainder.

Hints

- Insert zero-coefficient terms so like powers stay aligned. - Long division stops when the remainder's degree is less than the divisor's degree. - Subtract the entire product at each stage, including signs.

Solution

1. Write the dividend with missing terms: \(x^4+0x^3+2x^2+0x-3\). 2. Divide \(x^4\) by \(x^2\) to get \(x^2\). Subtract \(x^2(x^2-x+1)\), leaving \(x^3+x^2-3\). 3. Divide \(x^3\) by \(x^2\) to get \(x\). Subtract \(x(x^2-x+1)\), leaving \(2x^2-x-3\). 4. Divide \(2x^2\) by \(x^2\) to get \(2\). Subtract \(2(x^2-x+1)\), leaving \(x-5\). 5. Because the remainder has degree less than \(2\), the quotient is \(x^2+x+2\) and the remainder is \(x-5\).

Answer

Quotient: \(x^2+x+2\); remainder: \(x-5\)
Polynomial long and synthetic division 32
A polynomial \(P(x)\) has divisor \(x+3\), quotient \(2x^2-x+4\), and remainder \(-5\). a) Construct \(P(x)\) in standard form. b) Check your result by evaluating \(P(-3)\).

Hints

- Reverse the division identity to reconstruct the dividend. - Expand the divisor-quotient product before adding the remainder. - The check value comes from the zero of the divisor \(x+3\).

Solution

1. Use the division identity: \(P(x)=(x+3)(2x^2-x+4)-5\). 2. Expand \((x+3)(2x^2-x+4)=2x^3+5x^2+x+12\), so \(P(x)=2x^3+5x^2+x+7\). 3. Evaluate \(P(-3)=-54+45-3+7=-5\), which agrees with the stated remainder.

Answer

a) \(P(x)=2x^3+5x^2+x+7\) b) \(P(-3)=-5\)
Polynomial long and synthetic division 33
Elif wants to divide \(p(x)=x^3+3x^2-x-6\) by \(x+2\). Elif uses synthetic value \(2\) and concludes that the remainder is \(12\), so \(x+2\) is not a factor. Identify the setup error and perform the synthetic division correctly.

Hints

- Relate the synthetic value to the zero of the linear divisor. - Check the sign carefully before starting the synthetic-division arithmetic. - Use the final remainder to check the factor conclusion.

Solution

1. The divisor \(x+2\) is \(x-(-2)\), so the correct synthetic value is \(-2\), not \(2\). 2. Use coefficients \(1,3,-1,-6\). Bring down \(1\); multiply by \(-2\) and add to get \(1\); multiply by \(-2\) and add to get \(-3\); multiply by \(-2\) and add to get remainder \(0\). 3. The quotient is \(x^2+x-3\), the remainder is \(0\), and \(x+2\) is a factor.

Answer

Elif used the wrong synthetic value. The correct value is \(-2\), giving quotient \(x^2+x-3\) and remainder \(0\).
Polynomial long and synthetic division 34
Use repeated synthetic division to determine the multiplicity of the zero \(x=1\) for \(f(x)=x^4-x^3-3x^2+5x-2\). Then write the complete factorization of \(f\).

Hints

- Use the same synthetic value repeatedly while the remainder stays \(0\). - Each successful division removes one copy of the corresponding linear factor. - Stop when the next quotient no longer evaluates to \(0\) at the same value.

Solution

1. Use synthetic value \(1\) with coefficients \(1,-1,-3,5,-2\). The quotient coefficients are \(1,0,-3,2\) with remainder \(0\), so one factor \(x-1\) is removed. 2. Divide the quotient again by \(x-1\): using coefficients \(1,0,-3,2\) gives quotient \(x^2+x-2\) with remainder \(0\). 3. Divide once more by \(x-1\): using coefficients \(1,1,-2\) gives quotient \(x+2\) with remainder \(0\). 4. The remaining quotient has value \(3\) at \(x=1\), so it is not divisible by \(x-1\) again. Therefore, \(x=1\) has multiplicity \(3\). 5. The complete factorization is \(f(x)=(x-1)^3(x+2)\).

Answer

The zero \(x=1\) has multiplicity \(3\), and \(f(x)=(x-1)^3(x+2)\).
Polynomial long and synthetic division 35
When a polynomial \(P(x)\) is divided by \(x-2\), the quotient is \(x^3-3x+1\) and the remainder is \(5\). a) Construct \(P(x)\) in standard form. b) Use synthetic division to divide your polynomial by \(x+1\). c) Verify both remainders by evaluating \(P\) at the appropriate values.

Hints

- Reverse the division identity to construct the polynomial. - For the second division, pay attention to the sign in \(x+1\). - Check each remainder by substituting the zero of its divisor.

Solution

1. Use the division identity: \(P(x)=(x-2)(x^3-3x+1)+5=x^4-2x^3-3x^2+7x+3\). 2. For \(x+1\), use synthetic value \(-1\) with coefficients \(1,-2,-3,7,3\). The quotient is \(x^3-3x^2+7\) and the remainder is \(-4\). 3. Evaluate \(P(2)=5\) and \(P(-1)=-4\); both agree with the division remainders.

Answer

a) \(P(x)=x^4-2x^3-3x^2+7x+3\) b) Quotient \(x^3-3x^2+7\); remainder \(-4\) c) \(P(2)=5\) and \(P(-1)=-4\)
Polynomial long and synthetic division 36
A polynomial \(P(x)\) is divided by \(x^2+1\). The quotient is \(2x^2-x+3\), and the remainder is \(r(x)\). You also know that \(P(1)=11\) and \(P(-1)=5\). Determine \(r(x)\) without first reconstructing the entire polynomial \(P(x)\). Explain why the remainder must have the form you use.

Hints

- Start with the degree restriction on a remainder when the divisor is quadratic. - Use \(P(x)=d(x)q(x)+r(x)\) at each of the two given x-values. - The two evaluations give two conditions on the two coefficients of the remainder.

Solution

1. Because the divisor has degree \(2\), the remainder must have degree less than \(2\). Write \(r(x)=ax+b\). 2. The division identity is \(P(x)=(x^2+1)(2x^2-x+3)+ax+b\). 3. At \(x=1\), the divisor-quotient product equals \(8\), so \(a+b=11-8=3\). 4. At \(x=-1\), the divisor-quotient product equals \(12\), so \(-a+b=5-12=-7\). 5. Solving the two equations gives \(a=5\) and \(b=-2\). Therefore, \(r(x)=5x-2\).

Answer

\(r(x)=5x-2\)
Polynomial long and synthetic division 37
A school stage has a rectangular platform \((x+2)\,\text{ft}\) wide and \((mx+b)\,\text{ft}\) long, where \(m\) and \(b\) are constants. A ramp beside it takes up a fixed amount of floor space and does not overlap the platform. Together they cover \(A(x)=(2x^2+7x+11)\,\text{ft}^2\), where \(x>0\). Divide \(A(x)\) by \(x+2\) using polynomial long division. Find the platform's length and the ramp's area from the quotient and remainder.

Hints

- What product of the first quotient term and the width cancels the \(x^2\) term? - Subtract that product from the total area, then continue dividing. - How does the division identity separate the rectangular area from the leftover fixed area?

Solution

1. Divide the leading term: \(2x^2\div x=2x\). Subtract \((x+2)(2x)=2x^2+4x\) from \(A(x)\) to leave \(3x+11\). 2. Divide \(3x\div x=3\). Subtract \(3(x+2)=3x+6\) to leave remainder \(5\). 3. Thus \(A(x)=(x+2)(2x+3)+5\). The quotient \(2x+3\) gives the platform's length in feet, and the remainder \(5\) is the ramp's area in square feet.

Answer

Quotient: \(2x+3\), so the platform's length is \((2x+3)\,\text{ft}\). Remainder: \(5\), so the ramp's area is \(5\,\text{ft}^2\).
Polynomial long and synthetic division 38
A storage box has base sides \((x+2)\,\text{in}\) and \((x+3)\,\text{in}\). Its volume is \(V(x)=(2x^3+13x^2+27x+18)\,\text{in}^3\), for \(x>0\). Show the polynomial long division to find the box's height. Check by multiplying the base area by the height.

Hints

- First express the area of the rectangular base as one polynomial. - Which term should the quotient start with when you divide the leading terms? - Multiply the resulting height by the base area to check the volume.

Solution

1. The base area is \((x+2)(x+3)=x^2+5x+6\) square inches. 2. Divide \(V(x)\) by \(x^2+5x+6\). The first quotient term is \(2x\); subtracting \(2x^3+10x^2+12x\) leaves \(3x^2+15x+18\). 3. The next quotient term is \(3\). Subtracting \(3x^2+15x+18\) leaves remainder \(0\). 4. The height is \((2x+3)\,\text{in}\). Checking: \((x^2+5x+6)(2x+3)=2x^3+13x^2+27x+18\).

Answer

Divide by the base area \(x^2+5x+6\). Subtract \(2x(x^2+5x+6)\) to leave \(3x^2+15x+18\), then subtract \(3(x^2+5x+6)\) to leave \(0\). Quotient \(2x+3\); height \((2x+3)\,\text{in}\). Check: \((x^2+5x+6)(2x+3)=2x^3+13x^2+27x+18\).

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