# Thread: The Series

1. ## The Series

I'm doing the problem y'' + k^2 x^2 y = 0 on page 259 in the differential equations textbook and I got up to the part with the Recursive Formula. When I read your solution you said that a (n-2) term doesn't look very nice when you find all solutions right. Why and then you replaced all the n terms with n + 2. Why? I don't understand.

2. Look Here. (if $k\not = 0$).