25=-0,003x2+0,0638x+40

Solution for 25=-0,003x2+0,0638x+40 equation:

25=-0.003x^2+0.0638x+40

We move all terms to the left:

25-(-0.003x^2+0.0638x+40)=0

We get rid of parentheses

0.003x^2-0.0638x-40+25=0

We add all the numbers together, and all the variables

0.003x^2-0.0638x-15=0

a = 0.003; b = -0.0638; c = -15;
Δ = b2-4ac
Δ = -0.06382-4·0.003·(-15)
Δ = 0.18407044
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{-(-0.0638)-\sqrt{0.18407044}}{2*0.003}=\frac{0.0638-\sqrt{0.18407044}}{0.006}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-0.0638)+\sqrt{0.18407044}}{2*0.003}=\frac{0.0638+\sqrt{0.18407044}}{0.006}
$