(X+9)(x+5)=396

Solution for (X+9)(x+5)=396 equation:

(X+9)(X+5)=396

We move all terms to the left:

(X+9)(X+5)-(396)=0

We multiply parentheses ..

(+X^2+5X+9X+45)-396=0

We get rid of parentheses

X^2+5X+9X+45-396=0

We add all the numbers together, and all the variables

X^2+14X-351=0

a = 1; b = 14; c = -351;
Δ = b2-4ac
Δ = 142-4·1·(-351)
Δ = 1600
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$X_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$X_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{1600}=40$
$X_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(14)-40}{2*1}=\frac{-54}{2}
=-27
$
$X_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(14)+40}{2*1}=\frac{26}{2}
=13
$