dude please have a deep look in this section
http://targetiit.com/iit_jee_forum/posts/integration_siikho_2997.html
i hope that u will get the answers to ur problem there only
1st analyse if u still have doubts then ask again[1]
1.
 2.
3.

4.
5.
 n ε I+ and t is a parameter independant of x
hence show that 
dude please have a deep look in this section
http://targetiit.com/iit_jee_forum/posts/integration_siikho_2997.html
i hope that u will get the answers to ur problem there only
1st analyse if u still have doubts then ask again[1]