(7x-20)(4x+16)=180

Solution for (7x-20)(4x+16)=180 equation:

(7x-20)(4x+16)=180

We move all terms to the left:

(7x-20)(4x+16)-(180)=0

We multiply parentheses ..

(+28x^2+112x-80x-320)-180=0

We get rid of parentheses

28x^2+112x-80x-320-180=0

We add all the numbers together, and all the variables

28x^2+32x-500=0

a = 28; b = 32; c = -500;
Δ = b2-4ac
Δ = 322-4·28·(-500)
Δ = 57024
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:

$\sqrt{\Delta}=\sqrt{57024}=\sqrt{5184*11}=\sqrt{5184}*\sqrt{11}=72\sqrt{11}$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(32)-72\sqrt{11}}{2*28}=\frac{-32-72\sqrt{11}}{56}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(32)+72\sqrt{11}}{2*28}=\frac{-32+72\sqrt{11}}{56}
$