1.25x^2+2x-1=0

Solution for 1.25x^2+2x-1=0 equation:

1.25x^2+2x-1=0

a = 1.25; b = 2; c = -1;
Δ = b2-4ac
Δ = 22-4·1.25·(-1)
Δ = 9
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{9}=3$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(2)-3}{2*1.25}=\frac{-5}{2.5}
=-2
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(2)+3}{2*1.25}=\frac{1}{2.5}
=1/2.5
$