(4+x)(60+3x)=396

Solution for (4+x)(60+3x)=396 equation:

(4+x)(60+3x)=396

We move all terms to the left:

(4+x)(60+3x)-(396)=0

We add all the numbers together, and all the variables

(x+4)(3x+60)-396=0

We multiply parentheses ..

(+3x^2+60x+12x+240)-396=0

We get rid of parentheses

3x^2+60x+12x+240-396=0

We add all the numbers together, and all the variables

3x^2+72x-156=0

a = 3; b = 72; c = -156;
Δ = b2-4ac
Δ = 722-4·3·(-156)
Δ = 7056
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{7056}=84$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(72)-84}{2*3}=\frac{-156}{6}
=-26
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(72)+84}{2*3}=\frac{12}{6}
=2
$