Question

(2X^2+1/x)^6的展开式中常数项是?

Answer 1

60

C(6,k) (2x^2)^k (1/x)^(6-k) =C(6,k)2^k x^(2k) (1/x)^(6-k)=C(6,k)2^k x^(3k-6)

只有k=2时为常数,并且常数项为C(6,2)2^2=6*5/2 *2^2=60