The professor wrote the differential equation f²/f'=1 on the blackboard, and asked the students to solve it.

Everybody started working with the usual methods, except for a kid at the back of the class, who happened to have skipped that material, but was very bright.

Can you solve this equation without any integration?

Combining Oskar's approach with my observation that the equation is the same as -(1/f)'=1, assuming that- 1/f is a power series immediately gives the result that -1/f=c+x.

Posted by Richard on 2006-05-02 20:01:41