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 . The product is k2 – k + .

Answer 1

1. (k-9)(k-9)

2. 18

3. 81

Answer 2

$(a-b)^2=a^2-2ab+b^2\\\\(k-9)^2=k^2-2\cdot k\cdot9+9^2=k^2-18k+81$