10(x-20)(2x-20)=8320

Solution for 10(x-20)(2x-20)=8320 equation:

10(x-20)(2x-20)=8320

We move all terms to the left:

10(x-20)(2x-20)-(8320)=0

We multiply parentheses ..

10(+2x^2-20x-40x+400)-8320=0

We multiply parentheses

20x^2-200x-400x+4000-8320=0

We add all the numbers together, and all the variables

20x^2-600x-4320=0

a = 20; b = -600; c = -4320;
Δ = b2-4ac
Δ = -6002-4·20·(-4320)
Δ = 705600
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{705600}=840$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-600)-840}{2*20}=\frac{-240}{40}
=-6
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-600)+840}{2*20}=\frac{1440}{40}
=36
$