X2+0.4x=1.92

Solution for X2+0.4x=1.92 equation:

X2+0.4X=1.92

We move all terms to the left:

X2+0.4X-(1.92)=0

We add all the numbers together, and all the variables

X^2+0.4X-1.92=0

a = 1; b = 0.4; c = -1.92;
Δ = b2-4ac
Δ = 0.42-4·1·(-1.92)
Δ = 7.84
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{-(0.4)-\sqrt{7.84}}{2*1}=\frac{-0.4-\sqrt{7.84}}{2}
$
$X_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(0.4)+\sqrt{7.84}}{2*1}=\frac{-0.4+\sqrt{7.84}}{2}
$