Y=-0.004x^2+1.15x

Solution for Y=-0.004x^2+1.15x equation:

=-0.004Y^2+1.15Y

We move all terms to the left:

-(-0.004Y^2+1.15Y)=0

We get rid of parentheses

0.004Y^2-1.15Y=0

a = 0.004; b = -1.15; c = 0;
Δ = b2-4ac
Δ = -1.152-4·0.004·0
Δ = 1.3225
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$Y_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$Y_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$Y_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-1.15)-\sqrt{1.3225}}{2*0.004}=\frac{1.15-\sqrt{1.3225}}{0.008}
$
$Y_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-1.15)+\sqrt{1.3225}}{2*0.004}=\frac{1.15+\sqrt{1.3225}}{0.008}
$