2x^2-4x-20=90

Solution for 2x^2-4x-20=90 equation:

2x^2-4x-20=90

We move all terms to the left:

2x^2-4x-20-(90)=0

We add all the numbers together, and all the variables

2x^2-4x-110=0

a = 2; b = -4; c = -110;
Δ = b2-4ac
Δ = -42-4·2·(-110)
Δ = 896
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

The end solution:

$\sqrt{\Delta}=\sqrt{896}=\sqrt{64*14}=\sqrt{64}*\sqrt{14}=8\sqrt{14}$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-4)-8\sqrt{14}}{2*2}=\frac{4-8\sqrt{14}}{4}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-4)+8\sqrt{14}}{2*2}=\frac{4+8\sqrt{14}}{4}
$