hi

I am having a bit of trouble on the following integration problems and was wondering if anybody could help me out.

1) Integrate: ( x^2 ) / sqrt(9- x^2 ) dx

I think this one deals with trig substitution, but I am unsure of the exact method

2) Integrate: dx/(x^2 * sqrt(1 + x^2 ))

3) Integrate: x^2 / ( 25 + x ^2 ) dx

with 2 & 3, I'm really not sure of the method to start them. any help is appreciated; thanks alot!