Question

How do you simplify `(4x+9y) (4x-9y)`?

Answer 1

`(4x+9y)(4x-9y)=color(blue)(16x^2-81y^2)`

Explanation:

In general:
`color(white)("XXX")(a^2-b^2)=(a+b)(a-b)`

Evaluate with
`color(white)("XXX")a=4x`
and
`color(white)("XXX")b=9y`