What are the zeros of the function y = x2 + 10x - 171, and why?

To find the zeros, you have to factor the equation.

y = (x+19) (x-9)

This is because 19*-9=-171 and 19-9=10.

Now to make x=0, you have to make the equation

x+19=0

and x-9=0

To solve, isolate x on both equations.

This makes x=-19 and x=9.