Question

What are the zeros of the quadratic function f(x) = 8x2 – 16x – 15?

Answer 1

\(x=\dfrac{-b\pm\sqrt{b^2-4ac}}{2a}\)

Answer 2

do you understand how to use that?

Answer 3

the last two questions you posted were not "easily" factor-able, in in that situation it is best to either complete the square or use the quadratic equation. Most prefer the later over the former.