25=0.9621x+0.00038x^2

Solution for 25=0.9621x+0.00038x^2 equation:

25=0.9621x+0.00038x^2

We move all terms to the left:

25-(0.9621x+0.00038x^2)=0

We get rid of parentheses

-0.00038x^2-0.9621x+25=0

a = -0.00038; b = -0.9621; c = +25;
Δ = b2-4ac
Δ = -0.96212-4·(-0.00038)·25
Δ = 0.96363641
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{-(-0.9621)-\sqrt{0.96363641}}{2*-0.00038}=\frac{0.9621-\sqrt{0.96363641}}{-0.00076}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-0.9621)+\sqrt{0.96363641}}{2*-0.00038}=\frac{0.9621+\sqrt{0.96363641}}{-0.00076}
$