/sci/ - Science & Math

>>5912519
butt.....butt

/sci/ I know you hate help threads but could someone help me with this?
My professor is being a bit of a dick and refusing to help anyone.

Its a nonlinear ODE:
<span class="math">\ddot y + 2y(\dot y)^3 = 0[/spoiler]
I made the substitution
<span class="math">\dot y = z[/spoiler]
so then
<span class="math">\ddot y = z\frac{dz}{dy} [/spoiler]
so the equation becomes sperable and linear
<span class="math">z\frac{dz}{dy} +2yz^3 = 0[/spoiler]

But I think I keep fucking up the integration, I end up with
<span class="math">x = \frac{1}{3}y^3 + cy + d[/spoiler]
Would someone mind checking my work to see where I messed up?