(c-d)^2. (40+b)^2 (10+8k)^2 (5h-4)^2 (3a+1)^3 (4-a)^3 (b+3)(b-3) (k-y)+(k+y) (2c-a)(2c+a) (8x+4y)(8x-4y)
(c-d)2=c2-2cd+d2. (40+b)2=1600+80b+b2.