Y=5x^2-40x

Solution for Y=5x^2-40x equation:

=5Y^2-40Y

We move all terms to the left:

-(5Y^2-40Y)=0

We get rid of parentheses

-5Y^2+40Y=0

a = -5; b = 40; c = 0;
Δ = b2-4ac
Δ = 402-4·(-5)·0
Δ = 1600
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$Y_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$Y_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{1600}=40$
$Y_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(40)-40}{2*-5}=\frac{-80}{-10}
=+8
$
$Y_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(40)+40}{2*-5}=\frac{0}{-10}
=0
$