-y=5y^2-4

Solution for -y=5y^2-4 equation:

-y=5y^2-4

We move all terms to the left:

-y-(5y^2-4)=0

We add all the numbers together, and all the variables

-1y-(5y^2-4)=0

We get rid of parentheses

-5y^2-1y+4=0

a = -5; b = -1; c = +4;
Δ = b2-4ac
Δ = -12-4·(-5)·4
Δ = 81
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$y_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$y_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{81}=9$
$y_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-1)-9}{2*-5}=\frac{-8}{-10}
=4/5
$
$y_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-1)+9}{2*-5}=\frac{10}{-10}
=-1
$