Question 231741
there is actually a property to solve this, let me explain it first,ok?
(a+b)^2= a^2 +2ab+b^2

lets apply this in your problem:

(2x+8)^2 = (2x)^2+ 2(2*8) + (8)^2 = 4x^2 +32+64 =  4(x)^2 + 96