5x^2-20=10x

Solution for 5x^2-20=10x equation:

5x^2-20=10x

We move all terms to the left:

5x^2-20-(10x)=0

a = 5; b = -10; c = -20;
Δ = b2-4ac
Δ = -102-4·5·(-20)
Δ = 500
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:

$\sqrt{\Delta}=\sqrt{500}=\sqrt{100*5}=\sqrt{100}*\sqrt{5}=10\sqrt{5}$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-10)-10\sqrt{5}}{2*5}=\frac{10-10\sqrt{5}}{10}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-10)+10\sqrt{5}}{2*5}=\frac{10+10\sqrt{5}}{10}
$