Chapter P - Section P.5 - Factoring Polynomials - Exercise Set - Page 69: 120

$a.\quad x^{2}+y^{2}+2xy$ $ b.\quad (x+y)^{2}$

$a.$ We have a square with side length $x,$a square with side length $y,$ and two rectangles with sides $x$ and $y$ $A=x^{2}+y^{2}+2xy$ $b.$ We recognize this as a square of a sum $(A+B)^{2}=A^{2}+2AB+B^{2}$ $=(x+y)^{2}$