Question

Perfect square trinomial: (a – b)2 = (a – b)(a – b) = a2 – 2ab + b2 Find the product of (k – 9)2 using the perfect square trinomial rule shown on the left. The product (k – 9)2 can also be written as

Answer 1

K^2 - 2(9)k + 9^2

Or 

k^2 - 18k + 81

Just sub in k for a and 9 for b.