x2+22x+21=0

Solution for x2+22x+21=0 equation:

x2+22x+21=0

We add all the numbers together, and all the variables

x^2+22x+21=0

a = 1; b = 22; c = +21;
Δ = b2-4ac
Δ = 222-4·1·21
Δ = 400
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{400}=20$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(22)-20}{2*1}=\frac{-42}{2}
=-21
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(22)+20}{2*1}=\frac{-2}{2}
=-1
$