Question

How do you multiply `(2r^2+7s^2)(2r^2-7s^2)`?

Answer 1

`4r^4 -49s^4`

Explanation:

We could use the usual method of binomial times binomial, but we should notice that this is the answer to the difference of squares.

`(x+y)(x-y) = x^2 - y^2`

Therefore in this case:

`(2r^2+7s^2)(2r^2-7s^2) = 4r^4 -49s^4`