(30-4x)(16+2x)=396

Solution for (30-4x)(16+2x)=396 equation:

(30-4x)(16+2x)=396

We move all terms to the left:

(30-4x)(16+2x)-(396)=0

We add all the numbers together, and all the variables

(-4x+30)(2x+16)-396=0

We multiply parentheses ..

(-8x^2-64x+60x+480)-396=0

We get rid of parentheses

-8x^2-64x+60x+480-396=0

We add all the numbers together, and all the variables

-8x^2-4x+84=0

a = -8; b = -4; c = +84;
Δ = b2-4ac
Δ = -42-4·(-8)·84
Δ = 2704
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{2704}=52$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-4)-52}{2*-8}=\frac{-48}{-16}
=+3
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-4)+52}{2*-8}=\frac{56}{-16}
=-3+1/2
$