# Re-writing a PDE

1. Nov 13, 2014

### joshmccraney

1. The problem statement, all variables and given/known data
Provide the missing steps to re-write the equation into one with just two terms $$u_{tt} - c^2(u_{rr}+\frac{2}{r}u_r) = 0$$

2. Relevant equations
Nothing, other than this looks similar to the wave equation hybrid. (I'm just speculating)
Also, I'm a little uncertain what is being asked.

3. The attempt at a solution
Well nothing comes to mind. I am looking at this term: $u_{rr}+{2}u_r/{r}$. So far nothing huge is coming to mind. I initially tried something like $(u_r/r)'$ and then $(u_r \ln r)'$ since they looked close to the above but nothing helps. Any creative ideas out there?

Thanks a ton

2. Nov 13, 2014

### ZetaOfThree

Try multiplying both sides by $r^2$.

3. Nov 13, 2014

### joshmccraney

Brilliant! Thanks a ton!