0.4x+9x2=10

Solution for 0.4x+9x2=10 equation:

0.4x+9x^2=10

We move all terms to the left:

0.4x+9x^2-(10)=0

a = 9; b = 0.4; c = -10;
Δ = b2-4ac
Δ = 0.42-4·9·(-10)
Δ = 360.16
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{360.16}}{2*9}=\frac{-0.4-\sqrt{360.16}}{18}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(0.4)+\sqrt{360.16}}{2*9}=\frac{-0.4+\sqrt{360.16}}{18}
$