Question

How do you solve `4x=x^2-45`?

Answer 1

`(x - 9)(x + 4)`

Explanation:

It is a quadratic, so make it equal to 0.

`x^2 - 4x - 45 =0`

Find the factors of 45 which subtract to give 4.
The signs in the bracket are different - the greater factor will be negative.

`9 xx 5 = 45 and 9 -5 = 4`

`(x - 9)(x + 4)`