Answer
a. $x(x+y)-y(x+y)$
b. $(x+y)(x-y)$
Work Step by Step
a. Area of the shaded region = (Area of the rectangle whose sides are x,x+y) - (Area of the small rectangle whose sides are y, x+y)
$= x(x+y) - y(x+y)$ or
Take out common factor
$= (x+y)(x - y) $
$= x^{2}-y^{2} $
b. In factored form
$= x(x+y) - y(x+y)$
Take out common factor
$= (x+y)(x - y) $
