Question

How do you factor `z^2+9z-90`?

Answer 1

`z^2+9z-90=(z+15)(z-6)`

Explanation:

to find each number after `z`, you would need to find 2 numbers that:
add to the multiple of `z`
multiply to become the unit number

in this case, the 2 numbers need to add to `9` and multiply to become `90`.

the numbers `15` and `-6` satisfy this:

`15 (+) -6 = 15 - 6 = 9`
`15 * -6 = -90`

`therefore` `z^2+9z-90=(z+15)(z-6)`