Rules to use
Rule 1: x^2 = x*x
Rule 2: (a+b)*(c+d) = a*(c+d)+b*(c+d)
Rule 3: a*(b+c) = a*b+a*c
Using those rules, we get the following
(6+u)^2 = (6+u)*(6+u) ... use rule 1
(6+u)^2 = 6*(6+u)+u*(6+u) ... use rule 2
(6+u)^2 = 6*6+6*u+u*6+u*u ... use rule 3
(6+u)^2 = 36+6u+6u+u^2 ... multiply
(6+u)^2 = u^2+12u+36 ... combine like terms and rearrange
Answer: u^2+12u+36
