72x-3x^2=240

Solution for 72x-3x^2=240 equation:

72x-3x^2=240

We move all terms to the left:

72x-3x^2-(240)=0

a = -3; b = 72; c = -240;
Δ = b2-4ac
Δ = 722-4·(-3)·(-240)
Δ = 2304
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{2304}=48$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(72)-48}{2*-3}=\frac{-120}{-6}
=+20
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(72)+48}{2*-3}=\frac{-24}{-6}
=+4
$