a1=1,a10=3，a2a3a4a5a6a7a8a9=a1^8 乘以 q^36 而a10=3 即a10=a1 乘以 q^9所以a2a3a4a5a6a7a8a9=81
因为a1*a10=a2*a9=a3*a8=a4*a7=a5*a6所以a2a3a4a5a6a7a8a9=1*3*1*3*1*3*1*3=81
a10=q^9=3a2a3a4a5a6a7a8a9=q^36=3^4=81
