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

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

-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}
$