Question

What are the x-intercepts of y=x^2+2x-15

Answer 1

`(-5,0)` and
`(3,0)`

Explanation:

Think about it.

What two numbers multiply to -15 and add up to 2?

The answers are 5 and -3.

So plug that into the factored form of a parabola.

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

To find the x-intercepts, plug in 0 for
`y`.

`(x+5)(x-3)=0`

Since we are multiplying, at least one of the terms has to equal 0.

`x+5=0 \\ x-3=0 \\ \\ x=-5,3`

So the x-intercepts are
`(-5,0)` and
`(3,0)`.