(x+2)(x+18)-7x=0

Solution for (x+2)(x+18)-7x=0 equation:

(x+2)(x+18)-7x=0

We add all the numbers together, and all the variables

-7x+(x+2)(x+18)=0

We multiply parentheses ..

(+x^2+18x+2x+36)-7x=0

We get rid of parentheses

x^2+18x+2x-7x+36=0

We add all the numbers together, and all the variables

x^2+13x+36=0

a = 1; b = 13; c = +36;
Δ = b2-4ac
Δ = 132-4·1·36
Δ = 25
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{25}=5$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(13)-5}{2*1}=\frac{-18}{2}
=-9
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(13)+5}{2*1}=\frac{-8}{2}
=-4
$