Question

What is `(3 + sqrt2)(3 - sqrt2)`?

Answer 1

`(3+sqrt(2))(3-sqrt(2)) = 7`

Explanation:

Remember the difference of squares:
`color(white)("XXXX")` `(a^2-b^2) = (a+b)(a-b)`
and substitute
`color(white)("XXXX")` `3` for `a`
and
`color(white)("XXXX")` `sqrt(2)` for `b`