12e2∴ 综上所述:t≤.………………………………………………………9分
e2xf(x)?x≥2e, (Ⅲ)由(Ⅰ)可知,当x>0时,x12x∴ e≤2e (x>0), 1n11??2n22n2ne≤n2e. ∴ ne11111????????222232n?2ie2(e)3(e)n(e) i?ei?1∴
n1111(1?2?2?????2)23n ≤2e1111(1?2?2?????2)2?13?1n?1 <2e11111111111[1?(1?????????????)]2e232435n?2nn?1n?1 =
11111[1?(1???)]2e22nn?1 =
7<8e.………………………………………………………………14分
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