(1)已知等比数列{an}中,a1=36,a5=9⼀4,求q和Sn (2)等比数列{an}中,a

2025-06-28 00:15:17
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回答1:

a5=a1q^4
q^4=2^4
q=2
sn=36(2^n-1)
log3a1+log3a2+…+log3a10=20
log3a1a2a3……a10=20
log3(a5a6)^5=20
log3(a5a6)=4
a5a6=3^4=81