Question

How do you multiply `(k + 3)(k – 3)`?

Answer 1

`k^2-9`
This is a difference of squares where:
`(x^2-y^2) = (x+y)(x-y)`

If we let `x=k` and `y=3`
`((k)^2-(3)^2) = (k+3)(k-3)`