-15x2=-90

Solution for -15x2=-90 equation:

-15x^2=-90

We move all terms to the left:

-15x^2-(-90)=0

We add all the numbers together, and all the variables

-15x^2+90=0

a = -15; b = 0; c = +90;
Δ = b2-4ac
Δ = 02-4·(-15)·90
Δ = 5400
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:

$\sqrt{\Delta}=\sqrt{5400}=\sqrt{900*6}=\sqrt{900}*\sqrt{6}=30\sqrt{6}$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(0)-30\sqrt{6}}{2*-15}=\frac{0-30\sqrt{6}}{-30}
=-\frac{30\sqrt{6}}{-30}
=-\frac{\sqrt{6}}{-1}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(0)+30\sqrt{6}}{2*-15}=\frac{0+30\sqrt{6}}{-30}
=\frac{30\sqrt{6}}{-30}
=\frac{\sqrt{6}}{-1}
$