#2**+1 **

I'm going to explain ElectricPavolv's answer, which is indeed correct. He got the answer using his knowledge of **difference of squares**, which states that a quadratic equation in the form of a^2-b^2 = (a+b)(a-b). In this case, we substitute k for a and 9 for b, to get a factorization fo **(k-9)(k+9)**.

ThatOnePerson Nov 1, 2019