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The polynomial function \(f\) is defined by \(f(x) = x^3 - 2x^2 - 13x - 10\).
1. Find all zeros of \(f\). Use the fact that \(x = -1\) is a zero.
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 \(x - a\).
- Divide the polynomial by the known linear factor to reduce its degree.
- Factor the resulting quadratic expression.
- In complete factored form, the exponent on each factor gives the multiplicity.
Solution
1. Because \(x = -1\) is a zero, \(x + 1\) is a factor. Dividing gives \((x^3 - 2x^2 - 13x - 10) \div (x + 1) = x^2 - 3x - 10\).
2. Factor the quotient: \(x^2 - 3x - 10 = (x - 5)(x + 2)\). Therefore, the zeros are \(x = -2\), \(x = -1\), and \(x = 5\).
3. The factored form is \(f(x) = (x + 1)(x - 5)(x + 2)\).
4. 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.
