(x + 5)^2

(x+5)(x+5)

Foil
x^2 + 5 x + 5 x + 25 = x^2 + 10 x + 25

or use distributive property
x(x+5) + 5(x+5)
= x^2 + 5 x + 5 x + 25 = x^2+10x+25 again