X2-4x-8=5x

Solution for X2-4x-8=5x equation:

X2-4X-8=5X

We move all terms to the left:

X2-4X-8-(5X)=0

We add all the numbers together, and all the variables

X^2-9X-8=0

a = 1; b = -9; c = -8;
Δ = b2-4ac
Δ = -92-4·1·(-8)
Δ = 113
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$X_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$X_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$X_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-9)-\sqrt{113}}{2*1}=\frac{9-\sqrt{113}}{2}
$
$X_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-9)+\sqrt{113}}{2*1}=\frac{9+\sqrt{113}}{2}
$