已知数列{an}、{bn}满足an=2n,bn=lgan,如果bn＞30,求n的取值范围.（lg2=0.301

已知数列{a_n}、{b_n}满足a_n=2ⁿ,b_n=lga_n,如果b_n＞30,求n的取值范围.（lg2=0.301 0)

答案

解析：b_n=lga_n=lg2ⁿ=nlg2.

∵b_n＞30,即nlg2＞30,

∴n＞.

而

且∴n≥100.

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已知数列{an}、{bn}满足an=2n,bn=lgan,如果bn＞30,求n的取值范围.（lg2=0.301

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