If $\displaystyle {f}$ is the (constant) focal length of a convex lens and an object is placed at a distance $\displaystyle {p}$ from the lens, then its image will be at a distance $\displaystyle {q}$ from the lens, where $\displaystyle {f}$, $\displaystyle {p}$, and $\displaystyle {q}$ are related by the lens equation
$\displaystyle {\frac{{{1}}}{{{f}}}}={\frac{{{1}}}{{{p}}}}+{\frac{{{1}}}{{{q}}}}$

What is the rate of change of $\displaystyle {p}$ with respect to $\displaystyle {q}$ if $\displaystyle {q}={3}$ and $\displaystyle {f}={2}$? (Make sure you have the correct sign for the rate.)

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