x^2-21.9x+4=0

Solution for x^2-21.9x+4=0 equation:

x^2-21.9x+4=0

a = 1; b = -21.9; c = +4;
Δ = b2-4ac
Δ = -21.92-4·1·4
Δ = 463.61
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{-(-21.9)-\sqrt{463.61}}{2*1}=\frac{21.9-\sqrt{463.61}}{2}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-21.9)+\sqrt{463.61}}{2*1}=\frac{21.9+\sqrt{463.61}}{2}
$