3y4 = 28y2 - 9

3y4 = 28y2 - 9

I'm assuming you mean this:


3 y^4 = 28y^2 - 9


Start by substituting a new variable for y^2. If we let w = y^2, then this becomes


3w^2 = 28y -9


You can rearrange to get this into a standard quadratic form, then use the quadratic formula to solve for w. There will be two soultions for w. Then finally y = sqrt(w), but be careful to check whether both positive and negative values of sqrt(w) work in the original equation.