Y=4x2-256

Solution for Y=4x2-256 equation:

=4Y^2-256

We move all terms to the left:

-(4Y^2-256)=0

We get rid of parentheses

-4Y^2+256=0

a = -4; b = 0; c = +256;
Δ = b2-4ac
Δ = 02-4·(-4)·256
Δ = 4096
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$Y_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$Y_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{4096}=64$
$Y_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(0)-64}{2*-4}=\frac{-64}{-8}
=+8
$
$Y_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(0)+64}{2*-4}=\frac{64}{-8}
=-8
$