So sánh 2 p/số
\(A=\dfrac{2014^{2013}+1}{2014^{2014}+1};B=\dfrac{2014^{2012}+1}{2014^{2013}+1}\)
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2)Ta có: \(2^{332}< 2^{333}=\left(2^3\right)^{111}=8^{111}\)
\(3^{223}>3^{222}=\left(3^2\right)^{111}=9^{111}\)
Vì \(8^{111}< 9^{111}\) mà \(2^{332}< 8^{111},3^{223}>9^{111}\) nên suy ra \(2^{332}< 3^{223}\)
Vậy \(2^{332}< 3^{223}\)
1) \(A=\dfrac{10^{2013}+1}{10^{2014}+1}\Rightarrow10A=\dfrac{10^{2014}+10}{10^{2014}+1}=\dfrac{10^{2014}+1}{10^{2014}+1}+\dfrac{9}{10^{2014}+1}=1+\dfrac{9}{10^{2014}+1}\)
\(B=\dfrac{10^{2014}+1}{10^{2015}+1}\Rightarrow10B=\dfrac{10^{2015}+10}{10^{2015}+1}=\dfrac{10^{2015}+1}{10^{2015}+1}+\dfrac{9}{10^{2015}+1}=1+\dfrac{9}{10^{2015}+1}\)Vì: \(10^{2014}+1< 10^{2015}+1\Rightarrow\dfrac{9}{10^{2014}+1}>\dfrac{9}{10^{2015}+1}\Rightarrow1+\dfrac{9}{10^{2014}+1}>1+\dfrac{9}{10^{2015}+1}\)
Nên suy ra \(10A>10B\Rightarrow A>B\)
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
ta có: \(A=\frac{2014^{2013}+1}{2014^{2013}-1}=\frac{2014^{2013}-1+2}{2014^{2013}-1}=1+\frac{2}{2014^{2013}-1}\)
\(B=\frac{2014^{2013}-1}{2014^{2013}-3}=\frac{2014^{2013}-3+2}{2014^{2013}-3}=1+\frac{2}{2014^{2013}-3}\)
\(\Rightarrow\frac{2}{2014^{2013}-1}< \frac{2}{2014^{2013}-3}\)
\(\Rightarrow1+\frac{2}{2014^{2013}-1}< 1+\frac{2}{2014^{2013}-3}\)
=> A < B
Tổng S có 50 phân số
=> S > 1/100 + 1/100 + 1/100 +...+ 1/100 (50 phân số) => S > 1/2.
Vậy S > 1/2
Có \(2004A=\frac{2014^{2015}+2014}{2014^{2015}+1}=\frac{2014^{2015}+1+2013}{2014^{2015}+1}=1+\frac{2013}{2014^{2015}+1}\)
\(2014B=\frac{2014^{2014}+2014}{2014^{2014}+1}=\frac{2014^{2014}+1+2013}{2014^{2014}+1}=1+\frac{2013}{2014^{2014}+1}\)
Vì \(\frac{2013}{2014^{2015}+1}< \frac{2013}{2014^{2014}+1}\)
=> \(1+\frac{2013}{2014^{2015}+1}< 1+\frac{2013}{2014^{2014}+1}\)
=> \(A< B\)
\(A=\dfrac{2014^{2013}+1}{2014^{2014}+1}\Leftrightarrow2014A=\dfrac{2014^{2014}+2014}{2014^{2014}+1}=\dfrac{2014^{2014}+1+2013}{2014^{2014}+1}=1+\dfrac{2013}{2014^{2014}+1}\)
\(B=\dfrac{2014^{2012}+1}{2014^{2013}+1}\Leftrightarrow2014B=\dfrac{2014^{2013}+2014}{2014^{2013}+1}=\dfrac{2014^{2013}+1+2013}{2014^{2013}+1}=1+\dfrac{2013}{2014^{2013}+1}\)
Dễ thấy: \(1+\dfrac{2013}{2014^{2014}+1}< 1+\dfrac{2013}{2014^{2013}+1}\) nên \(2014A< 2014B\) hay \(A< B\)
Thầy phynit, cô @Cẩm Vân Nguyễn Thị, các bạn hok giỏi Toán: @Nguyễn Huy Tú, @Nguyễn Trần Thành Đạt, ..................
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