(4x^2/(3x^2+2))dx=(4/3) + (8/9)/(x^2+(2/3))dx积分得(4/3)x+(8/9)(√3/√2)arctan[(√3/√2)x] + C(x^5/(根号x^3+1))=(1/3)x^3/√(x^3+1) dx^3令u=x^3原式=(1/3)u/√(u+1) du=(1/3)[√(u+1) -...=(1/3)x^3/√(x^3+1) dx^3请问前面的1/3是怎么出来的dx^3=3x^2dx所以x^2dx=(1/3)dx^3