T6=C(n,5)*2^5*x^5T7=C(n,6)*2^6^x^6第6项与第7项的系数相等∴C(n,5)*2^5=C(n,6)*2^6∴C(n,5)=2C(n,6)∴n!/[5!(n-5)!]=2*n!/[6!(n-6)!]∴ (n-5)!=3(n-6)!∴n-5=3,∴n=8Tr+1=C(8,r)2^r*x^r由 C(8,r-1)*2^(r-1)≤ C(8,...