To determine the scale factor used in the dilation of line segment \(AB\) with a center point of dilation at the origin, we can use the coordinates of points \(A\) and \(B\) before dilation and points \(A'\) and \(B'\) after dilation.
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Identify the coordinates:
- Point \(A\) has coordinates \(A(9, 9)\).
- Point \(B\) has coordinates \(B(6, 6)\).
- Point \(A'\) has coordinates \(A'(3, 3)\).
- Point \(B'\) has coordinates \(B'(2, 2)\).
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Calculate the scale factor: The scale factor \(k\) can be calculated using the formula \[ k = \frac{\text{New coordinate}}{\text{Original coordinate}}. \]
For point \(A\), \[ k_A = \frac{A'(x)}{A(x)} = \frac{3}{9} = \frac{1}{3}. \]
For point \(B\), \[ k_B = \frac{B'(x)}{B(x)} = \frac{2}{6} = \frac{1}{3}. \]
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Conclusion: The scale factor is consistent for both points and is \( \frac{1}{3} \).
Thus, the scale factor used in the dilation of line segment \(AB\) is negative \( \frac{1}{3} \).
The correct answer is negative \( \frac{1}{3} \).