x^2+5x-10x-66=0

Solution for x^2+5x-10x-66=0 equation:

x^2+5x-10x-66=0

We add all the numbers together, and all the variables

x^2-5x-66=0

a = 1; b = -5; c = -66;
Δ = b2-4ac
Δ = -52-4·1·(-66)
Δ = 289
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{289}=17$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-5)-17}{2*1}=\frac{-12}{2}
=-6
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-5)+17}{2*1}=\frac{22}{2}
=11
$