165=5x^2

Solution for 165=5x^2 equation:

165=5x^2

We move all terms to the left:

165-(5x^2)=0

a = -5; b = 0; c = +165;
Δ = b2-4ac
Δ = 02-4·(-5)·165
Δ = 3300
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:

$\sqrt{\Delta}=\sqrt{3300}=\sqrt{100*33}=\sqrt{100}*\sqrt{33}=10\sqrt{33}$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(0)-10\sqrt{33}}{2*-5}=\frac{0-10\sqrt{33}}{-10}
=-\frac{10\sqrt{33}}{-10}
=-\frac{\sqrt{33}}{-1}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(0)+10\sqrt{33}}{2*-5}=\frac{0+10\sqrt{33}}{-10}
=\frac{10\sqrt{33}}{-10}
=\frac{\sqrt{33}}{-1}
$