n^2-21n-100=0

Solution for n^2-21n-100=0 equation:

n^2-21n-100=0

a = 1; b = -21; c = -100;
Δ = b2-4ac
Δ = -212-4·1·(-100)
Δ = 841
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$n_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$n_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{841}=29$
$n_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-21)-29}{2*1}=\frac{-8}{2}
=-4
$
$n_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-21)+29}{2*1}=\frac{50}{2}
=25
$