X^2-0.1x-1=0

Solution for X^2-0.1x-1=0 equation:

X^2-0.1X-1=0

a = 1; b = -0.1; c = -1;
Δ = b2-4ac
Δ = -0.12-4·1·(-1)
Δ = 4.01
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{-(-0.1)-\sqrt{4.01}}{2*1}=\frac{0.1-\sqrt{4.01}}{2}
$
$X_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-0.1)+\sqrt{4.01}}{2*1}=\frac{0.1+\sqrt{4.01}}{2}
$