Bài 1: So sánh phân số: \(\frac{2^{2014}+1}{2^{2014}}\) và\(\frac{2^{2014+2}}{2^{2014+1}}\)
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Gợi ý nhé: bạn hãy so sánh 2014A và 2014B rồi suy ngược lại A và B
Ta có:
2014A=20142014+ 2014/20142014+1=1+2013/20142014+1
2014B=20142013+2014/20142013+1=1+2013/20142013+1
vì 1+2013/20142014+1<1+2013/20142013+1 nên 10A < 10B
suy ra A<B
\(\frac{2^{2014}+1}{2^{2014}}=\frac{2^{2014}}{2^{2014}}+\frac{1}{2^{2014}}=1+\frac{1}{2^{2014}}\)
\(\frac{2^{2014}+2}{2^{2014}+1}=\frac{2^{2014}+1+1}{2^{2014}+1}=\frac{2^{2014}+1}{2^{2014}+1}+\frac{1}{2^{2014}+1}=1+\frac{1}{2^{2014}+1}\)
so sánh \(\frac{1}{2^{2014}}\) và \(\frac{1}{2^{2014}+1}\)
ta có
\(2^{2014}<2^{2014}+1\)
nên \(\frac{1}{2^{2014}}>\frac{1}{2^{2014}+1}=>1+\frac{1}{2014}>1+\frac{1}{2014+1}=>\frac{2^{2014}+1}{2^{2014}}>\frac{2^{2014}+2}{2^{2014}+1}\)
ta thấy:
2^2014<2^2014+2
=>\(\frac{2^{2014}+1}{2^{2014}}>\frac{2^{2014}+1}{2^{2014}+2}\)
vậy......
Có : 22014 + 1 > 22014 nên \(\frac{2^{2014}+1}{2^{2014}}\)> 1 .
22104 + 1 < 22014 + 2 nên \(\frac{2^{2014}+1}{2^{2014}+2}\)< 1.
=> \(\frac{2^{2014}+1}{2^{2014}}\)>\(\frac{2^{2014}+1}{2^{2014}+2}\)
Đặt :
\(A=\frac{2^{2014}+1}{2^{2014}}=\frac{2^{2014}}{2^{2014}}+\frac{1}{2^{2014}}=1+\frac{1}{2^{2014}}\)
\(B=\frac{2^{2014}+2}{2^{2014}+1}=\frac{2^{2014}+1+1}{2^{2014}+1}=\frac{2^{2014}+1}{2^{2014}+1}\)\(=1+\frac{1}{2^{2014}+1}\)
\(1+\frac{1}{2^{2014}}>1+\frac{1}{2^{2014}+2}\Leftrightarrow A>B\)
Ta có : A = \(\frac{2^{2014}+1}{2^{2014}}=1+\frac{1}{2^{2014}}\)
B = \(\frac{2^{2014}+2}{2^{2014}+1}=1+\frac{1}{2^{2014}+1}\)
Vì : \(\frac{1}{2^{2014}}>\frac{1}{2^{2014}+1}\)
Nên A > B
\(\frac{2^{2014}+2}{2^{2014}+1}=\frac{2^{2014}+1+1}{2^{2014}+1}=1+\frac{1}{2^{2014}+1}\)
\(\frac{2^{2014}+1}{2^{2014}}=1+\frac{1}{2^{2014}}\)
Do \(2^{2014}+1>2^{2014}\Rightarrow\frac{1}{2^{2014}+1}<\frac{1}{2^{2014}}\Rightarrow1+\frac{1}{2^{2014}+1}<1+\frac{1}{2^{2014}}\Rightarrow\frac{2^{2014}+2}{2^{2014}+1}<\frac{2^{2014}+1}{2^{2014}}\)
Đặt A= 2015^2013+1/2015^2014+7, B=2015^2014-2/2015^2015-2
2015A= 2015^2014+2015/2015^2014+7= 1 + (2008/2015^2014+7)
2015B= 2015^2015-4030/2015^2015-2= 1 - (4028/2015^2015-2)
Do 2015A>1>2015B nên A>B
bên trái nhỏ hơn bên phải
Ta có : \(\frac{2^{2014+2}}{2^{2014+1}}=\frac{2^{2014}.2^2}{2^{2014}.2}=2\)
\(\frac{2^{2014}+1}{2^{2014}}=1+\frac{1}{2^{2014}}< 2\)
Vậy : \(\frac{2^{2014}+1}{2^{2014}}< \frac{2^{2014+2}}{2^{2014+1}}\)