y=x(arcsinx/3)+(9-x^2)^1/2+ln2
dy=(arcsinx/3)dx+xd(arcsinx/3)-x/(9-x^2)^1/2dx
=[(arcsinx/3)+x/(9-x^2)^1/2-x/(9-x^2)^1/2]dx
=(arcsinx/3)dxxd(arcsinx/3)是怎么化出来的呢？明白了~