Question

How do you factor `y=x^2 - 2x - 15` ?

Answer 1

`y=(x-5)(x+3)`

Explanation:

`"the factors of - 15 which sum to - 2 are - 5 and + 3"`

`y=(x-5)(x+3)`

Answer 2

`(x-5)(x+3)`

Explanation:

First, find two numbers that have a sum of -2 (the second term) and have a product of -15 (the third term)
Multiples of 15:
1 | 15
3 | 5
`-5 * 3 = -15` and `-5 + 3 = -2`
Use this to "split the middle" of the polynomial
`x^2 - 5x + 3x - 15`
Factor
`x(x-5) + 3(x-5)`
`(x-5)(x+3)`