0=21x^2-180x-300

Solution for 0=21x^2-180x-300 equation:

0=21x^2-180x-300

We move all terms to the left:

0-(21x^2-180x-300)=0

We add all the numbers together, and all the variables

-(21x^2-180x-300)=0

We get rid of parentheses

-21x^2+180x+300=0

a = -21; b = 180; c = +300;
Δ = b2-4ac
Δ = 1802-4·(-21)·300
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*-21}=\frac{-420}{-42}
=+10
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(180)+240}{2*-21}=\frac{60}{-42}
=-1+3/7
$