问题
填空题
各项均为正数的等比数列{an}满足a1a7=4,a6=8,函数f(x)=a1x+a2x2+a3x3+…+a10x10,则f(
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答案
∵正数的等比数列{an}满足a1a7=4,∴
=4,可得a4=2,a 24
∵a6=8,
∴
=q2,可得q2=4,可得q=2,∴a1×q3=2,得a1=a6 a4
,1 4
∴an=a1×qn=
×2n-1=2n-3,1 4
∴f(x)=a1x+a2x2+a3x3+…+a10x10,
∴f(
)=a11 2
+a21 2
2+a3(1 2
)3+…+a10(1 2
)10=1 2
+1 23
+…+1 23
=10×1 23
=1 23
=10 8
,5 4
故答案为
;5 4