求定积分要有上下限的,否则是求不定积分.对于 x/(1+√x) 可令 y=√x,y²=x,2ydy=dx∫x/(1+√x)dx=2∫y³dy/(1+y)而y³dy/(1+y)=(y³+1)/(1+y)-1/(1+y)=(y²-y+1)-1/(1+y)2∫y³dy/(1+y)2∫(...