(x+6)^2
(c-12)^2
(14+3x)^2
(15-a)^2
(a-1)(a+1)
(c+11)(c-11)
(12-3a)^2

(x+6)²   = x²+12x+36

(c-12)²=   c²-24c+144

(14+3x)²=196+84x+9x²

(15-a)²= 225-30a+a²

(a-1)(a+1)=a²-1

(c+11)(c-11)=c^2-121

(12-3a)²=144 – 72a+9a²