Question

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

Answer 1

Answer:

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

Step-by-step 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 $(3,0)$.