Question

How do you factor completely `81x^2 – 100`?

Answer 1

`(9x+10)(9x-10)`

Explanation:

To factor `81x^2-100` we must first recognize that this is the difference (subtraction) of two perfect squares.

`81x^2 = (9x)(9x)`
`100=(10)(10)`

When we factors the difference of two squares the binomials always have one `+` and one `-`.

`(9x+10)(9x-10)`