(4x+20)(7x+5)=180

Solution for (4x+20)(7x+5)=180 equation:

(4x+20)(7x+5)=180

We move all terms to the left:

(4x+20)(7x+5)-(180)=0

We multiply parentheses ..

(+28x^2+20x+140x+100)-180=0

We get rid of parentheses

28x^2+20x+140x+100-180=0

We add all the numbers together, and all the variables

28x^2+160x-80=0

a = 28; b = 160; c = -80;
Δ = b2-4ac
Δ = 1602-4·28·(-80)
Δ = 34560
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

The end solution:

$\sqrt{\Delta}=\sqrt{34560}=\sqrt{2304*15}=\sqrt{2304}*\sqrt{15}=48\sqrt{15}$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(160)-48\sqrt{15}}{2*28}=\frac{-160-48\sqrt{15}}{56}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(160)+48\sqrt{15}}{2*28}=\frac{-160+48\sqrt{15}}{56}
$