Answer
a. $9x^{2}-16$
b. $(3x+4)(3x-4)$
Work Step by Step
a. Area of the shaded region = (Area of the square whose side is $3x$) - $4 \times $(Area of the square whose side is 2)
$=(3x)^{2} - 4 (2)^{2}$
$=9x^{2} - 16$
b. In factored form
To factor the difference of the squares, use the formula
$(a^{2}-b^{2}) = (a+b)(a-b)$
$9x^{2} - 16 = (3x)^{2} - 4^{2} = (3x+4)(3x-4)$
