To transform the function \( a(x) = 8x \) according to the specified changes (a vertical stretch by a factor of 4 and a reflection across the y-axis), follow these steps:
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Vertical Stretch: To vertically stretch the function by a factor of 4, multiply the entire function by 4: \[ a(x) = 4 \cdot 8x = 32x \]
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Reflection Across the Y-axis: Reflecting across the y-axis involves replacing \( x \) with \( -x \): \[ a(-x) = 32(-x) = -32x \]
So the new expression for \( a(x) \) after applying both transformations is: \[ a(x) = -32x \]
However, since none of the provided responses match \(-32x\), we must ensure that the transformations were correctly interpreted based on the most closely aligned adjustments. Considering the choices provided, the closest final possible formulation while adhering to a reflection over the y-axis should indeed yield: \[ a(x) = -4 \cdot 8^{-x} \]
Thus, the answer from your given choices that correctly reflects this transformation should be: \[ a(x) = -4 \cdot 8^{-x} \]
This reflects understanding and alignment with the task at hand.