y*4y=780

Solution for y*4y=780 equation:

y*4y=780

We move all terms to the left:

y*4y-(780)=0

Wy multiply elements

4y^2-780=0

a = 4; b = 0; c = -780;
Δ = b2-4ac
Δ = 02-4·4·(-780)
Δ = 12480
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$y_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$y_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

The end solution:

$\sqrt{\Delta}=\sqrt{12480}=\sqrt{64*195}=\sqrt{64}*\sqrt{195}=8\sqrt{195}$
$y_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(0)-8\sqrt{195}}{2*4}=\frac{0-8\sqrt{195}}{8}
=-\frac{8\sqrt{195}}{8}
=-\sqrt{195}
$
$y_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(0)+8\sqrt{195}}{2*4}=\frac{0+8\sqrt{195}}{8}
=\frac{8\sqrt{195}}{8}
=\sqrt{195}
$