(2x+12)(2x+18)=391

Solution for (2x+12)(2x+18)=391 equation:

(2x+12)(2x+18)=391

We move all terms to the left:

(2x+12)(2x+18)-(391)=0

We multiply parentheses ..

(+4x^2+36x+24x+216)-391=0

We get rid of parentheses

4x^2+36x+24x+216-391=0

We add all the numbers together, and all the variables

4x^2+60x-175=0

a = 4; b = 60; c = -175;
Δ = b2-4ac
Δ = 602-4·4·(-175)
Δ = 6400
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{6400}=80$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(60)-80}{2*4}=\frac{-140}{8}
=-17+1/2
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(60)+80}{2*4}=\frac{20}{8}
=2+1/2
$