900=15x^2

Solution for 900=15x^2 equation:

900=15x^2

We move all terms to the left:

900-(15x^2)=0

a = -15; b = 0; c = +900;
Δ = b2-4ac
Δ = 02-4·(-15)·900
Δ = 54000
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:

$\sqrt{\Delta}=\sqrt{54000}=\sqrt{3600*15}=\sqrt{3600}*\sqrt{15}=60\sqrt{15}$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(0)-60\sqrt{15}}{2*-15}=\frac{0-60\sqrt{15}}{-30}
=-\frac{60\sqrt{15}}{-30}
=-\frac{2\sqrt{15}}{-1}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(0)+60\sqrt{15}}{2*-15}=\frac{0+60\sqrt{15}}{-30}
=\frac{60\sqrt{15}}{-30}
=\frac{2\sqrt{15}}{-1}
$