Question

integrate x/(x^2+1)dx ?

Answer 1

http://www.wolframalpha.com/input/?i=integrate+x%2F%28x^2%2B1%29dx

Answer 2

try
\[u=x^2+1\]
\[du=2xdx\]
\[\frac{1}{2}du=dx\] then
\[\frac{1}{2}\int \frac{1}{u}du\]
get
\[\frac{1}{2}\ln(u)\]