# Using substiution of the form v=1/y^k to solve 1st order DE

1. Nov 15, 2009

### useruseruser

$$xy'+3y+4y^3=0$$
use substitution of the form $$v=1/y^k$$ for some positive integer k. Choose a value of k that cancels the y^3 term.

2. Nov 16, 2009

### HallsofIvy

Staff Emeritus
Well, have you tried at all? There's not a whole lot of deep thinking involved! Just do exactly what they tell you to do. If [tex]v= 1/y^k[/itex], then $y= 1/v^{1/k}$. Find the derivative of y and plug it and y into the equation. There should be a single value of k that simplifies the equation.

Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook