2400+20x-x2=0

Solution for 2400+20x-x2=0 equation:

2400+20x-x2=0

We add all the numbers together, and all the variables

-1x^2+20x+2400=0

a = -1; b = 20; c = +2400;
Δ = b2-4ac
Δ = 202-4·(-1)·2400
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*-1}=\frac{-120}{-2}
=+60
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(20)+100}{2*-1}=\frac{80}{-2}
=-40
$