0=2x^2+21x-100

Solution for 0=2x^2+21x-100 equation:

0=2x^2+21x-100

We move all terms to the left:

0-(2x^2+21x-100)=0

We add all the numbers together, and all the variables

-(2x^2+21x-100)=0

We get rid of parentheses

-2x^2-21x+100=0

a = -2; b = -21; c = +100;
Δ = b2-4ac
Δ = -212-4·(-2)·100
Δ = 1241
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-21)-\sqrt{1241}}{2*-2}=\frac{21-\sqrt{1241}}{-4}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-21)+\sqrt{1241}}{2*-2}=\frac{21+\sqrt{1241}}{-4}
$