9x^2-120x-225=0

Solution for 9x^2-120x-225=0 equation:

9x^2-120x-225=0

a = 9; b = -120; c = -225;
Δ = b2-4ac
Δ = -1202-4·9·(-225)
Δ = 22500
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{22500}=150$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-120)-150}{2*9}=\frac{-30}{18}
=-1+2/3
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-120)+150}{2*9}=\frac{270}{18}
=15
$