Answer
$8x+16$
Work Step by Step
The area of the shaded region is the area of the big rectangle minus the area of the unshaded smaller rectangle.
Thus, the area $A_1$ of the big rectangle is:
$A_1=(x+4)(x+4)=x^2+8x+16$
and the area $A_2$ of unshaded region is:
$A_2=x\cdot x=x^2$.
Thus, the shaded area is:
$A_1-A_2=x^2+8x+16-x^2=8x+16$.
