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\(A=\left(-\frac{1}{2013}-\frac{3}{11^2}-\frac{5}{11^3}-\frac{3}{11^4}\right)-\frac{4}{11^4};B=\left(-\frac{1}{2013}-\frac{3}{11^2}-\frac{5}{11^3}-\frac{3}{11^2}\right)-\frac{4}{11^2}\)
Vì 114 > 112 nên \(\frac{4}{11^4}-\frac{4}{11^2}\) => A > B
Ta có : \(A=\frac{11^{2007}+1}{11^{2008}+1}=\frac{11\left[11^{2007}+1\right]}{11^{2008}+1}=\frac{11^{2008}+11}{11^{2008}+1}=\frac{11^{2008}+1+10}{11^{2008}+1}=1+\frac{10}{11^{2008}+1}\)
\(B=\frac{11^{2008}+1}{11^{2009}+1}=\frac{11\left[11^{2008}+1\right]}{11^{2009}+1}=\frac{11^{2009}+11}{11^{2009}+1}=\frac{11^{2009}+1+10}{11^{2009}+1}=1+\frac{10}{11^{2009}+1}\)
Đến đây bạn tự so sánh nhé
Ta có: B = 11^2008+1/11^2009+1 < 11^20087 +1 + 10/11^2009+1+10 = 11^2008+11/11^2009+11 = 11(11^2007 +1)/11(11^2008+1) = 11^2007 +1/11^2008+1 = A
=>B <A
Vậy A > B
Ta có :
\(A=\frac{10^{11}-1}{10^{12}-1}< \frac{10^{11}-1+11}{10^{12}-1+11}=\frac{10^{11}+10}{10^{12}+10}=\frac{10\left(10^{10}+1\right)}{10\left(10^{11}+1\right)}=\frac{10^{10}+1}{10^{11}+1}=B\)
\(\Rightarrow A< B\)
\(A=\frac{10^{11}-1}{10^{12}-1}< \frac{10^{11}-1+11}{10^{12}-1+11}\) theo công thức \(\frac{a}{b}< \frac{a+m}{b+m}\)
\(A< \frac{10^{11}+10}{10^{12}+10}=\frac{10^{10}\left(10+1\right)}{10^{11}\left(10+1\right)}=\frac{10^{10}}{10^{11}}\)
\(\Rightarrow\frac{10^{10}}{10^{11}}=\frac{10^{10}\cdot10^{12}}{10^{11}\cdot10^{12}}=\frac{10^{22}}{10^{23}}\)
\(\Leftrightarrow A< \frac{10^{10}}{10^{11}}=\frac{10^{11}}{10^{12}}\)
Lại áp dụng công thức \(\frac{a}{b}< \frac{a+m}{b+m}\)
\(A< \frac{10^{10}}{10^{11}}=\frac{10^{11}}{10^{12}}< \frac{10^{11}+1}{10^{12}+1}=B\)
\(\Leftrightarrow A< B\)
Hoặc \(A< \frac{10^{11}-1+2}{10^{12}-1+2}=\frac{10^{12}+1}{10^{12}+1}\)
..... (EZ)
\(A=\frac{11^{40}+1}{11^{43}+1}\)
\(11^3A=\frac{11^3\left(11^{40}+1\right)}{11^{43}+1}=\frac{11^{43}+1331}{11^{43}+1}=\frac{11^{43}+1+1330}{11^{43}+1}=\frac{11^{43}+1}{11^{43}+1}+\frac{1330}{11^{43}+1}=1+\frac{1330}{11^{43}+1}\)
\(B=\frac{11^{41}+1}{11^{44}+3}\)
\(11^3B=\frac{11^3\left(11^{41}+1\right)}{11^{44}+3}=\frac{11^{44}+1331}{11^{44}+3}=\frac{11^{44}+3+1328}{11^{44}+3}=\frac{11^{44}+3}{11^{44}+3}+\frac{1328}{11^{44}+3}=1+\frac{1328}{11^{44}+3}\)
Ta có: \(\frac{1330}{11^{43}+1}>\frac{1330}{11^{44}+3}>\frac{1328}{11^{44}+3}\)
\(\Rightarrow\frac{1330}{11^{43}+1}>\frac{1328}{11^{44}+3}\)
\(\Rightarrow1+\frac{1330}{11^{43}+1}>1+\frac{1328}{11^{44}+3}\)
\(\Rightarrow11^3A>11^3B\)
\(\Rightarrow A>B\)
Vậy \(A>B\)
P/s: Hoq chắc :<