Answer
$3+\sqrt r$
Work Step by Step
Multiply $\frac{3+\sqrt r}{3+\sqrt r}$ to the expression, we have:
$\frac{9-r}{3-\sqrt r}\cdot \frac{3+\sqrt r}{3+\sqrt r}=\frac{(9-r)(3+\sqrt r)}{9-r}=3+\sqrt r$
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