Answer
True.
Work Step by Step
As $y$ is bounded by $y=g_{2}(x)$ and $y=g_{1}(x),$ we should have $g_{1}(x) \leq y \leq g_{2}(x)$
\[
\int_{a}^{b} \int_{g_{1}(x)}^{g_{2}(x)} f(x, y) d y d x=\iint_{R} f(x, y) d A
\]
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