> and if it is proper to set this then equal to zero > to give a new equation that could be merged with the original to get rid > of the cumbersome XY terms - then that i failed to do.
What? To find extreme values of y, set y' = 0. That gives you two equations to solve for x and y with the additional requirement that 4y^3 - 2ay + 4x^2 y - bx /= 0
> I've tried completing squares etc but can not get rid of composite XY > terms. > Complete the square on 4x^3 + 2ax + 4xy^2 - by = 0 to get y in terms of x and then substitue y = f(x) into the first equation and solve for x.
That's a heafty task. Next, get values for y and check to see if they satisfy the addional requirement and then if they're maximal, miminal or points of inflection.
> If I could eliminate X and get a generalised Y-Only equation > then I could manage the rest. > > Any help would be appreciated > > Mervyn Mc Crabbe >