Question

How do you multiply `(x + 5)(x - 4)`?

Answer 1

`x^2 + x - 20`

Explanation:

To multiply two polynomials, you should use the FOIL (first outside inside last) method.

`(x+5)(x-4) = underbrace(x * x)_(color(blue)("first")) + underbrace(x * (-4))_(color(blue)("outside")) + underbrace(5 * x)_(color(blue)("inside")) + underbrace(5 * (-4))_(color(blue)("last"))`

`(x+5)(x-4) = x^2 - 4x + 5x - 20`

Simplify the last equation to get the answer:

`x^2 + x - 20`