Answer:
H. 9
Step-by-step explanation:
Using the difference of 2 squares formula, we get (x - y)(x + y)=12
Divide each side by x - y: x + y = 12/(x - y)
But x - y = 4, so replace x - y by 4: x + y = 12/4 = 3
Because x^2 + 2xy + y^2 = (x + y)^2, so we take our equation exponent by 2:
(x + y)^2 = 3^2 = 9
x^2 + 2xy + y^2 = 9
