0=50+21x-x^2

Solution for 0=50+21x-x^2 equation:

0=50+21x-x^2

We move all terms to the left:

0-(50+21x-x^2)=0

We add all the numbers together, and all the variables

-(50+21x-x^2)=0

We get rid of parentheses

x^2-21x-50=0

a = 1; b = -21; c = -50;
Δ = b2-4ac
Δ = -212-4·1·(-50)
Δ = 641
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{641}}{2*1}=\frac{21-\sqrt{641}}{2}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-21)+\sqrt{641}}{2*1}=\frac{21+\sqrt{641}}{2}
$