240+20x-10x^2=0

Solution for 240+20x-10x^2=0 equation:

240+20x-10x^2=0

a = -10; b = 20; c = +240;
Δ = b2-4ac
Δ = 202-4·(-10)·240
Δ = 10000
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{10000}=100$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(20)-100}{2*-10}=\frac{-120}{-20}
=+6
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(20)+100}{2*-10}=\frac{80}{-20}
=-4
$