2a^2-20a=-4

Solution for 2a^2-20a=-4 equation:

2a^2-20a=-4

We move all terms to the left:

2a^2-20a-(-4)=0

We add all the numbers together, and all the variables

2a^2-20a+4=0

a = 2; b = -20; c = +4;
Δ = b2-4ac
Δ = -202-4·2·4
Δ = 368
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$a_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$a_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

The end solution:

$\sqrt{\Delta}=\sqrt{368}=\sqrt{16*23}=\sqrt{16}*\sqrt{23}=4\sqrt{23}$
$a_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-20)-4\sqrt{23}}{2*2}=\frac{20-4\sqrt{23}}{4}
$
$a_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-20)+4\sqrt{23}}{2*2}=\frac{20+4\sqrt{23}}{4}
$