Question

-8x^2+4x+5=0 using quadratic formula

Answer 1

So you want to solve for x?

It would be nice if this would easily factor:
(-4x + 5)(2x +1)  = 0    This will not work!

So you need to use the quadratic formula:
a = -8, b = 4, c = 5

$x = \frac{-b+/- \sqrt{b^{2}-4ac} }{2a}$

x = (-4 +/- $\sqrt{16-4(-8)(5)}$)/2(-8)
   = (-4 +/- $\sqrt{16 + 160}$)/-16
   = (-4 +$\sqrt{176}$)/-16
   = 1/4 - $\sqrt{11}$/4