20x^2-72x-140=0

Solution for 20x^2-72x-140=0 equation:

20x^2-72x-140=0

a = 20; b = -72; c = -140;
Δ = b2-4ac
Δ = -722-4·20·(-140)
Δ = 16384
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{16384}=128$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-72)-128}{2*20}=\frac{-56}{40}
=-1+2/5
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-72)+128}{2*20}=\frac{200}{40}
=5
$