0=2100+180x-3x^2

Solution for 0=2100+180x-3x^2 equation:

0=2100+180x-3x^2

We move all terms to the left:

0-(2100+180x-3x^2)=0

We add all the numbers together, and all the variables

-(2100+180x-3x^2)=0

We get rid of parentheses

3x^2-180x-2100=0

a = 3; b = -180; c = -2100;
Δ = b2-4ac
Δ = -1802-4·3·(-2100)
Δ = 57600
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{57600}=240$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-180)-240}{2*3}=\frac{-60}{6}
=-10
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-180)+240}{2*3}=\frac{420}{6}
=70
$