x(x+-15)+x+x+-2=120

Solution for x(x+-15)+x+x+-2=120 equation:

x(x+-15)+x+x+-2=120

We move all terms to the left:

x(x+-15)+x+x+-2-(120)=0

determiningTheFunctionDomain
x(x+-15)+x+x-2-120+=0

We add all the numbers together, and all the variables

x(x-15)+x+x-2-120+=0

We add all the numbers together, and all the variables

2x+x(x-15)=0

We multiply parentheses

x^2+2x-15x=0

We add all the numbers together, and all the variables

x^2-13x=0

a = 1; b = -13; c = 0;
Δ = b2-4ac
Δ = -132-4·1·0
Δ = 169
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{169}=13$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-13)-13}{2*1}=\frac{0}{2}
=0
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-13)+13}{2*1}=\frac{26}{2}
=13
$