T(r+1)=C(n,r)a^(n-r)b^r
=>
T(r+1)=C(8,r)(ax)^(8-r)(-x^(-1/2)^r=[C(8,r)(a^(8)(-1)^r]x^(8-r-r/2)
=>8-3r/2=0
=>r=16/3
题有问题?r要为整数才对!
T(r+1)=C(n,r)a^(n-r)b^r
=>
T(r+1)=C(8,r)(ax)^(8-r)(-x^(-1/2)^r=[C(8,r)(a^(8)(-1)^r]x^(8-r-r/2)
=>8-3r/2=0
=>r=16/3
题有问题?r要为整数才对!