$$f(x) = -16x^2 + 80x + 5$$

I need to find the bigger value of $x$ that makes $f(x) = 0$.

Naturally, I thought to do:
$$0=-16x^2+80x+5$$
and I applied the quadratic formula

$$0=\frac{-80\pm\sqrt{6080}}{-32}$$
but the answer doesn't seem like it would be correct. Did I do something wrong?