-9a2=-90

Solution for -9a2=-90 equation:

-9a^2=-90

We move all terms to the left:

-9a^2-(-90)=0

We add all the numbers together, and all the variables

-9a^2+90=0

a = -9; b = 0; c = +90;
Δ = b2-4ac
Δ = 02-4·(-9)·90
Δ = 3240
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$a_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$a_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

The end solution:

$\sqrt{\Delta}=\sqrt{3240}=\sqrt{324*10}=\sqrt{324}*\sqrt{10}=18\sqrt{10}$
$a_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(0)-18\sqrt{10}}{2*-9}=\frac{0-18\sqrt{10}}{-18}
=-\frac{18\sqrt{10}}{-18}
=-\frac{\sqrt{10}}{-1}
$
$a_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(0)+18\sqrt{10}}{2*-9}=\frac{0+18\sqrt{10}}{-18}
=\frac{18\sqrt{10}}{-18}
=\frac{\sqrt{10}}{-1}
$