x^2+1.25x-20=0

Solution for x^2+1.25x-20=0 equation:

x^2+1.25x-20=0

a = 1; b = 1.25; c = -20;
Δ = b2-4ac
Δ = 1.252-4·1·(-20)
Δ = 81.5625
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{-(1.25)-\sqrt{81.5625}}{2*1}=\frac{-1.25-\sqrt{81.5625}}{2}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(1.25)+\sqrt{81.5625}}{2*1}=\frac{-1.25+\sqrt{81.5625}}{2}
$