Answer
a) $8x^2-2\pi x^2$
b) $(8-2\pi)x^2$
Work Step by Step
a) We write the area of the shaded blue region as the difference between the area of the rectangle and the areas of the two circles:
$$\begin{align*}
(4x)(2x)-2(\pi x^2)=8x^2-2\pi x^2.
\end{align*}$$
b) We factor the expression:
$$8x^2-2\pi x^2=(8-2\pi)x^2.$$
