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Ta có: A=\(\frac{10^{2006}+1}{10^{2007}+1}\)
=>10A=\(\frac{10\left(10^{2006}+1\right)}{10^{2007}+1}=\frac{10^{2007}+10}{10^{2007}+1}=1+\frac{9}{10^{2007}+1}\)
Ta có: B=\(\frac{10^{2007}+1}{10^{2008}+1}\)
=>10B=\(\frac{10\left(10^{2007}+1\right)}{10^{2008}+1}=\frac{10^{2008}+10}{10^{2008}+1}=1+\frac{9}{10^{2008}+1}\)
Mà \(\frac{9}{10^{2007}+1}>\frac{9}{10^{2008}+1}\) (do 102007+1<102008+1)
=>\(1+\frac{9}{10^{2007}+1}>1+\frac{9}{10^{2008}+1}\)
=>10A>10B
=>A>B
Áp dụng a/b < 1 => a/b < a+m/b+m (a,b,m thuộc N*)
=> \(B=\frac{10^{2007}+1}{10^{2008}+1}< \frac{10^{2007}+1+9}{10^{2008}+1+9}\)
=> \(B< \frac{10^{2007}+10}{10^{2008}+10}\)
=> \(B< \frac{10.\left(10^{2006}+1\right)}{10.\left(10^{2007}+1\right)}\)
=> \(B< \frac{10^{2006}+1}{10^{2007}+1}=A\)
Đặt \(A=\frac{10^{2006}+9}{10^{2007}+9}\)
\(\Rightarrow10A=\frac{10^{2007}+90}{10^{2007}+9}=1+\frac{81}{10^{2007}+9}\)
\(\frac{10^{2007}+9}{10^{2008}+9}=B\)
\(\Rightarrow10B=\frac{10^{2008}+90}{10^{2008}+9}=1+\frac{81}{10^{2008}+9}\)
Vì\(10A>10B\Rightarrow A>B\)
A=\(\frac{10^{2006}+1}{10^{2007}+1}\)
10.A=\(\frac{10.\left(10^{2006}+10\right)}{10^{2007}+1}\)
=\(1+\frac{9}{10^{2007}+1}\)
B=\(\frac{10^{2007}+1}{10^{2008}+1}\)
\(10.B=\frac{10.\left(10^{2007}+10\right)}{10^{2008}+1}\)
= \(1+\frac{9}{10^{2008}+1}\)
Vì\(1+\frac{9}{10^{2007}+1}>1+\frac{9}{10^{2008}+1}\) nên 10A > 10B \(\Rightarrow A>B\)
k cko mk nka
vì \(\frac{10^{2006}+1}{10^{2007}+1}\)<1
tc:B=\(\frac{10^{2006}+1}{10^{2007}+1}\)<\(\frac{10^{2006}+1+9}{10^{2007}+1+9}\)=\(\frac{10^{2006}+10}{10^{2007}+10}\)=\(\frac{10\left(10^{2005}+1\right)}{10\left(10^{2006}+1\right)}\)=\(\frac{10^{2005}+1}{10^{2006}+1}\)=A
=>B<A
A<B
quy tắc: a/b <1 thì a/b<a+m/b+m
a/b>1 thì a/b> a+m/b+m
Đặt A=\(\frac{10^{2006}+1}{10^{2007}+1}\);\(B=\frac{10^{2007}+1}{10^{2008}+1}\)
10A=\(\frac{10\left(10^{2006}+1\right)}{10^{2007}+1}\)=\(\frac{10^{2007}+1+9}{10^{2007}+1}\)
10B=\(\frac{10\left(10^{2007}+1\right)}{10^{2008}+1}=\frac{10^{2008}+1+9}{10^{2008}+1}\)
Vì \(\frac{9}{10^{2007}+1}>\frac{9}{10^{2008}+1}\)nên 10A>10B nên A>B