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Graph absolute value functions

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5335789
The dashed graph is \(f(x)=|x|\). The red graph \(g\) is a translation of \(f\). Describe the translation and write a rule for \(g(x)\).
Figure for problem 533578

Hints

- Locate the vertex of each V-shaped graph. - Horizontal translations change the expression inside the absolute value. - Vertical translations add or subtract a constant outside the absolute value.

Solution

1. The vertex of \(f\) is \((0, 0)\), and the vertex of \(g\) is \((-3, 1)\). 2. Moving the vertex from \((0, 0)\) to \((-3, 1)\) requires a shift left \(3\) units and up \(1\) unit. 3. A shift left \(3\) units replaces \(x\) with \(x+3\), and a shift up \(1\) unit adds \(1\) outside the absolute value. 4. Therefore, \(g(x)=|x+3|+1\).

Answer

Shift left \(3\) units and up \(1\) unit; \(g(x)=|x+3|+1\)
5262449
Let \(g(x)=4-|x|\). a) Describe the graph for \(-5\le x\le5\). b) Find the x-intercepts. c) Find the maximum point and justify your answer using the equation.

Hints

- Rewrite the absolute value function as two linear pieces if helpful. - An x-intercept occurs where \(g(x)=0\). - Use the fact that \(|x|\ge0\).

Solution

1. The graph of \(g(x)=4-|x|\) is an upside-down V with vertex \((0, 4)\). For \(x\ge0\), \(g(x)=4-x\); for \(x<0\), \(g(x)=4+x\). 2. Set \(4-|x|=0\). Then \(|x|=4\), so \(x=4\) or \(x=-4\). The x-intercepts are \((4, 0)\) and \((-4, 0)\). 3. Because \(|x|\ge0\), \(4-|x|\le4\). Equality occurs at \(x=0\), so the maximum point is \((0, 4)\).

Answer

a) An upside-down V with vertex \((0, 4)\) b) \((-4, 0)\) and \((4, 0)\) c) The maximum point is \((0, 4)\).
5340439
The blue graph is \(f(x)=|x|\), and the red graph is \(g\). Two students describe the change from \(f\) to \(g\). Tim says, “The graph is vertically compressed.” Sara says, “The graph is horizontally stretched.” 1) Determine the equation of \(g\). 2) Show mathematically how both descriptions can be correct, and state each scale factor.
Figure for problem 534043

Hints

- Use a point on the red graph to determine its coefficient. - Write a vertical scaling in the form \(af(x)\). - Write a horizontal scaling in the form \(f(bx)\). - Use the rule \(|ab|=|a||b|\) to compare the two expressions.

Solution

1. The red graph passes through \((2, 1)\). Using \(g(x)=a|x|\), substitute the point: \(1=a|2|\). Therefore, \(a=\frac{1}{2}\), so \(g(x)=\frac{1}{2}|x|\). 2. Tim describes a vertical compression by a factor of \(\frac{1}{2}\): \(g(x)=\frac{1}{2}f(x)\). 3. Sara describes a horizontal stretch by a factor of \(2\): \(g(x)=f\left(\frac{x}{2}\right)=\left|\frac{x}{2}\right|=\frac{1}{2}|x|\). 4. Both transformations produce the same function because absolute value is homogeneous for a positive scale factor.

Answer

1) \(g(x)=\frac{1}{2}|x|\) 2) Vertical compression factor: \(\frac{1}{2}\), since \(g(x)=\frac{1}{2}f(x)\); horizontal stretch factor: \(2\), since \(g(x)=f\left(\frac{x}{2}\right)\)
5340769
The blue graph is \(f(x)=|x+4|\). The red graph \(g\) is produced by a translation and a reflection. Describe the transformations and write \(g(x)\) in terms of \(f(x)\).
Figure for problem 534076

Hints

- Compare the vertices of the two V-shaped graphs. - Determine whether the red graph opens upward or downward. - Apply the horizontal change inside the input and the reflection outside.

Solution

1. The vertex of \(f\) is \((-4, 0)\), and the vertex of \(g\) is \((-2, 0)\). Therefore, the graph shifts right \(2\) units. 2. The blue graph opens upward, while the red graph opens downward, so the shifted graph is reflected across the x-axis. 3. A shift right \(2\) units gives \(f(x-2)\), and the reflection places a negative sign outside. 4. Therefore, \(g(x)=-f(x-2)=-|x+2|\).

Answer

Shift right \(2\) units and reflect across the x-axis; \(g(x)=-f(x-2)\)

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