Answer
a) $16x^2-4\pi x^2$
b) $4(4-\pi)x^2$
Work Step by Step
a) We write the area of the shaded blue region as the difference between the area of the square and the areas of the four circles:
$$\begin{align*}
(4x)(4x)-4(\pi x^2)=16x^2-4\pi x^2.
\end{align*}$$
b) We factor the expression:
$$16x^2-4\pi x^2=4(4-\pi)x^2.$$
