Question

Factor k^2-81...............

Answer 1

`(k+9)(k-9)`

Explanation:

`k^2-81`

`k^2-9^2`

Apply the difference of squares formula:
`x^2-y^2=\left(x+y\right)\left(x-y\right)`

Thus,
`k^2-9^2=\left(k+9\right)\left(k-9\right)`