x2-15x-216=0

Solution for x2-15x-216=0 equation:

x2-15x-216=0

We add all the numbers together, and all the variables

x^2-15x-216=0

a = 1; b = -15; c = -216;
Δ = b2-4ac
Δ = -152-4·1·(-216)
Δ = 1089
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{1089}=33$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-15)-33}{2*1}=\frac{-18}{2}
=-9
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-15)+33}{2*1}=\frac{48}{2}
=24
$