18=2x^2-6x

Solution for 18=2x^2-6x equation:

18=2x^2-6x

We move all terms to the left:

18-(2x^2-6x)=0

We get rid of parentheses

-2x^2+6x+18=0

a = -2; b = 6; c = +18;
Δ = b2-4ac
Δ = 62-4·(-2)·18
Δ = 180
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:

$\sqrt{\Delta}=\sqrt{180}=\sqrt{36*5}=\sqrt{36}*\sqrt{5}=6\sqrt{5}$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(6)-6\sqrt{5}}{2*-2}=\frac{-6-6\sqrt{5}}{-4}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(6)+6\sqrt{5}}{2*-2}=\frac{-6+6\sqrt{5}}{-4}
$