x2-1.25x-1.5=0

Solution for x2-1.25x-1.5=0 equation:

x2-1.25x-1.5=0

We add all the numbers together, and all the variables

x^2-1.25x-1.5=0

a = 1; b = -1.25; c = -1.5;
Δ = b2-4ac
Δ = -1.252-4·1·(-1.5)
Δ = 7.5625
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{7.5625}}{2*1}=\frac{1.25-\sqrt{7.5625}}{2}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-1.25)+\sqrt{7.5625}}{2*1}=\frac{1.25+\sqrt{7.5625}}{2}
$