A=-16x^2+64x

Solution for A=-16x^2+64x equation:

=-16A^2+64A

We move all terms to the left:

-(-16A^2+64A)=0

We get rid of parentheses

16A^2-64A=0

a = 16; b = -64; c = 0;
Δ = b2-4ac
Δ = -642-4·16·0
Δ = 4096
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$A_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$A_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{4096}=64$
$A_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-64)-64}{2*16}=\frac{0}{32}
=0
$
$A_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-64)+64}{2*16}=\frac{128}{32}
=4
$