x2+21x-80=0

Solution for x2+21x-80=0 equation:

x2+21x-80=0

We add all the numbers together, and all the variables

x^2+21x-80=0

a = 1; b = 21; c = -80;
Δ = b2-4ac
Δ = 212-4·1·(-80)
Δ = 761
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{761}}{2*1}=\frac{-21-\sqrt{761}}{2}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(21)+\sqrt{761}}{2*1}=\frac{-21+\sqrt{761}}{2}
$