(4x-10)(x+2)=80

Solution for (4x-10)(x+2)=80 equation:

(4x-10)(x+2)=80

We move all terms to the left:

(4x-10)(x+2)-(80)=0

We multiply parentheses ..

(+4x^2+8x-10x-20)-80=0

We get rid of parentheses

4x^2+8x-10x-20-80=0

We add all the numbers together, and all the variables

4x^2-2x-100=0

a = 4; b = -2; c = -100;
Δ = b2-4ac
Δ = -22-4·4·(-100)
Δ = 1604
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:

$\sqrt{\Delta}=\sqrt{1604}=\sqrt{4*401}=\sqrt{4}*\sqrt{401}=2\sqrt{401}$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-2)-2\sqrt{401}}{2*4}=\frac{2-2\sqrt{401}}{8}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-2)+2\sqrt{401}}{2*4}=\frac{2+2\sqrt{401}}{8}
$