4=-16x^2+41.6x

Solution for 4=-16x^2+41.6x equation:

4=-16x^2+41.6x

We move all terms to the left:

4-(-16x^2+41.6x)=0

We get rid of parentheses

16x^2-41.6x+4=0

a = 16; b = -41.6; c = +4;
Δ = b2-4ac
Δ = -41.62-4·16·4
Δ = 1474.56
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{-(-41.6)-\sqrt{1474.56}}{2*16}=\frac{41.6-\sqrt{1474.56}}{32}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-41.6)+\sqrt{1474.56}}{2*16}=\frac{41.6+\sqrt{1474.56}}{32}
$