15x^2+72x-15=0

Solution for 15x^2+72x-15=0 equation:

15x^2+72x-15=0

a = 15; b = 72; c = -15;
Δ = b2-4ac
Δ = 722-4·15·(-15)
Δ = 6084
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{6084}=78$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(72)-78}{2*15}=\frac{-150}{30}
=-5
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(72)+78}{2*15}=\frac{6}{30}
=1/5
$