x2-x-2,1=0

Solution for x2-x-2,1=0 equation:

x2-x-2.1=0

We add all the numbers together, and all the variables

x^2-1x-2.1=0

a = 1; b = -1; c = -2.1;
Δ = b2-4ac
Δ = -12-4·1·(-2.1)
Δ = 9.4
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)-\sqrt{9.4}}{2*1}=\frac{1-\sqrt{9.4}}{2}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-1)+\sqrt{9.4}}{2*1}=\frac{1+\sqrt{9.4}}{2}
$