-140=8x^2+72x

Solution for -140=8x^2+72x equation:

-140=8x^2+72x

We move all terms to the left:

-140-(8x^2+72x)=0

We get rid of parentheses

-8x^2-72x-140=0

a = -8; b = -72; c = -140;
Δ = b2-4ac
Δ = -722-4·(-8)·(-140)
Δ = 704
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:

$\sqrt{\Delta}=\sqrt{704}=\sqrt{64*11}=\sqrt{64}*\sqrt{11}=8\sqrt{11}$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-72)-8\sqrt{11}}{2*-8}=\frac{72-8\sqrt{11}}{-16}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-72)+8\sqrt{11}}{2*-8}=\frac{72+8\sqrt{11}}{-16}
$