x^2-3.5x+1.8=0

Solution for x^2-3.5x+1.8=0 equation:

x^2-3.5x+1.8=0

a = 1; b = -3.5; c = +1.8;
Δ = b2-4ac
Δ = -3.52-4·1·1.8
Δ = 5.05
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{-(-3.5)-\sqrt{5.05}}{2*1}=\frac{3.5-\sqrt{5.05}}{2}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-3.5)+\sqrt{5.05}}{2*1}=\frac{3.5+\sqrt{5.05}}{2}
$