0=-0.04x^2+8.3x+4.3

Solution for 0=-0.04x^2+8.3x+4.3 equation:

0=-0.04x^2+8.3x+4.3

We move all terms to the left:

0-(-0.04x^2+8.3x+4.3)=0

We add all the numbers together, and all the variables

-(-0.04x^2+8.3x+4.3)=0

We get rid of parentheses

0.04x^2-8.3x-4.3=0

a = 0.04; b = -8.3; c = -4.3;
Δ = b2-4ac
Δ = -8.32-4·0.04·(-4.3)
Δ = 69.578
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{-(-8.3)-\sqrt{69.578}}{2*0.04}=\frac{8.3-\sqrt{69.578}}{0.08}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-8.3)+\sqrt{69.578}}{2*0.04}=\frac{8.3+\sqrt{69.578}}{0.08}
$