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Ta dùng bất đẳng thức\(\frac{a}{b}<\frac{a+n}{b+n}\left(n\ne0\right)\)
Ta có \(B=\frac{10^{20}+1}{10^{21}+1}<\frac{10^{20}+1+9}{10^{21}+1+9}<\frac{10^{20}+10}{10^{21}+10}<\frac{10\left(10^{19}+1\right)}{10\left(10^{20}+1\right)}\)
\(<\frac{10^{19}+1}{10^{20}+1}\)
Vậy \(A>B\)
Ta có :
\(\frac{10^{20}+1}{10^{21}+1}< \frac{10^{20}+1+9}{10^{21}+1+9}=\frac{10^{20}+10}{10^{21}+10}=\frac{10\left(10^{19}+1\right)}{10\left(10^{20}+1\right)}=\frac{10^{19}+1}{10^{20}+1}\)
Vậy \(\frac{10^{19}+1}{10^{20}+1}>\frac{10^{20}+1}{10^{21}+1}\)
Ta có:\(B=\frac{10^{20}+1}{10^{21}+1}< 1\Rightarrow B=\frac{10^{20}+1}{10^{21}+1}< \frac{10^{20}+1+9}{10^{21}+1+9}=\frac{10^{20}+10}{10^{21}+10}=\frac{10\left(10^{19}+1\right)}{10\left(10^{20}+1\right)}=\frac{10^{19}+1}{10^{20}+1}=A\)
=> A > B
Ta có: \(10A=\frac{10^{20}+10}{10^{20}+1}=1+\frac{9}{10^{20}+1}\)
\(10B=\frac{10^{21}+10}{10^{21}+1}=1+\frac{9}{10^{21}+1}\)
Vì \(\frac{9}{10^{20}+1}>\frac{9}{10^{21}+1}\Rightarrow1+\frac{9}{10^{20}+1}>1+\frac{9}{10^{20}+1}\)
\(\Rightarrow10A>10B\)
\(\Rightarrow A>B\)
Vậy A > B
Ta có tính chất: \(\dfrac{a}{b}< \dfrac{a+m}{b+m}\)
\(N=\dfrac{10^{20}+1}{10^{21}+1}< \dfrac{10^{20}+1+9}{10^{21}+1+9}\)
\(\Rightarrow N< \dfrac{10^{20}+10}{10^{21}+10}\)
\(\Rightarrow N< \dfrac{10\left(10^{19}+1\right)}{10\left(10^{20}+1\right)}\)
\(\Rightarrow N< \dfrac{10^{19}+1}{10^{20}+1}\)
\(\Rightarrow N< M\)
Công thức a/b >1 => a/b > a+n/b+n (a, b,n \(\in\) N*)
B = 2010-1/2010-3 > 1 nên B = 2010-1/2010-3 > 2010-1+2/2010-3+2 = 2010+1/ 2010-1 = A
Vậy A < B