X2+21x=1100

Solution for X2+21x=1100 equation:

X2+21X=1100

We move all terms to the left:

X2+21X-(1100)=0

We add all the numbers together, and all the variables

X^2+21X-1100=0

a = 1; b = 21; c = -1100;
Δ = b2-4ac
Δ = 212-4·1·(-1100)
Δ = 4841
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{4841}}{2*1}=\frac{-21-\sqrt{4841}}{2}
$
$X_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(21)+\sqrt{4841}}{2*1}=\frac{-21+\sqrt{4841}}{2}
$