I am doing these questions from the kreyszig textbook: http://i.imgur.com/atP9Oah.jpg
For Q2, I did:
y^3*y' + x^3 =0
y^3 dy = -x^3 dx
taking the integral of both sides
y^4/4 = -x^4/4 + c
y^4 = -x^4 + c
Then I raised everything to 1/4 power.
leaving us with y = +- (c-x^4)^1/4
However, the wolfram also included an i and -i in front.
Why is that?
Additionally: I have no idea how to do Question 3. Any help would be appreciated.