chung to rang 1/5+1/6+1/7=...+1/16+1/17<2
Những câu hỏi liên quan
Cho B=1/5+1/6+1/7+...+1/17 .Chung to rang B<2
Chung minh rang 1/15+1/16+1/17+1/18+.....+1/44 > 5/6
Chung minh rang
1 be hon 1/5+1/6+.....+1/16+1/17 be hon 2
vì các phân số có mẫu lớn hơn tử thì bé hơn 1 nên chúng bé hơn 2
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Chung to 1< 1/5 + 1/6 +...+ 1/16 + 1/17<2
Chung to 1< 1/5 + 1/6 +...+1/16 + 1/17<2
Chung to 1< 1/5 + 1/6 +...+ 1/16 + 1/17<2
cho a=1=1\2+1\3-1\4+1\5...+1\49-1\50.Chung to rang 7\12<4<5\6
chung to rang tong B sau lon hon 1/2 B=1/12+1/13+1/14+1/15+1/16+1/17+1/18+1/19+1/20+1/21+1/22
chung to rang B= 1/2^2+1/3^2+1/4^2+1/5^2+1/6^2+1/7^2+1/8^2<1
B = 1/22 + 1/32 + 1/42 + 1/52 + 1/62 + 1/72 + 1/82 < 1/1.2 + 1/2.3 + 1/3.4 + 1/4.5 + 1/5.6 + 1/6.7 + 1/7.8
B = < 1 - 1/2 + 1/2 - 1/3 + 1/3 - 1/4 + 1/4 - 1/5 + 1/5 - 1/6 + 1/6 - 1/7 + 1/7 - 1/8
B = < 1 - 1/8 < 1
=> đpcm
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