X2+21x+98=0

Solution for X2+21x+98=0 equation:

X2+21X+98=0

We add all the numbers together, and all the variables

X^2+21X+98=0

a = 1; b = 21; c = +98;
Δ = b2-4ac
Δ = 212-4·1·98
Δ = 49
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$X_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$X_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{49}=7$
$X_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(21)-7}{2*1}=\frac{-28}{2}
=-14
$
$X_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(21)+7}{2*1}=\frac{-14}{2}
=-7
$