3n+1=n+6 解得n=2.5舍去
或3n+1+n+6=27 解得n=5
[x^(1/2)-2x^(-1/3)]^5
常数项是C(5,2)[x^(1/2)]²[-2x^(-1/3)]³=10*(-8)=-80
二项式 第12题
3n+1=n+6 解得n=2.5舍去
或3n+1+n+6=27 解得n=5
[x^(1/2)-2x^(-1/3)]^5
常数项是C(5,2)[x^(1/2)]²[-2x^(-1/3)]³=10*(-8)=-80