15x^2+90x-9=0

Solution for 15x^2+90x-9=0 equation:

15x^2+90x-9=0

a = 15; b = 90; c = -9;
Δ = b2-4ac
Δ = 902-4·15·(-9)
Δ = 8640
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:

$\sqrt{\Delta}=\sqrt{8640}=\sqrt{576*15}=\sqrt{576}*\sqrt{15}=24\sqrt{15}$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(90)-24\sqrt{15}}{2*15}=\frac{-90-24\sqrt{15}}{30}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(90)+24\sqrt{15}}{2*15}=\frac{-90+24\sqrt{15}}{30}
$