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$\frac{10^{101-1}}{10^{102-1}}$ và $\frac{10^{100+1}}{10^{101+1}}$
= $\frac{10^{100}}{10^{101}}$ và $\frac{10^{101}}{10^{102}}$
Mà $\frac{10^{100}}{10^{101}}$ < $\frac{10^{101}}{10^{102}}$
=> $\frac{10^{101-1}}{10^{102-1}}$ < $\frac{10^{100+1}}{10^{101+1}}$
\(a,\frac{x+1}{65}+\frac{x+2}{64}=\frac{x+3}{63}+\frac{x+4}{62}\)
\(\Rightarrow\left[\frac{x+1}{65}+1\right]+\left[\frac{x+2}{64}+1\right]=\left[\frac{x+3}{63}+1\right]+\left[\frac{x+4}{62}+1\right]\)
\(\Rightarrow\frac{x+1+65}{65}+\frac{x+2+64}{64}=\frac{x+3+63}{63}+\frac{x+4+62}{62}\)
\(\Rightarrow\frac{x+66}{65}+\frac{x+66}{64}=\frac{x+66}{63}+\frac{x+66}{62}\)
\(\Rightarrow\frac{x+66}{65}+\frac{x+66}{64}=\frac{x+66}{63}+\frac{x+66}{62}=0\)
\(\Rightarrow\left[x+66\right]\left[\frac{1}{65}+\frac{1}{64}-\frac{1}{63}+\frac{1}{62}\right]=0\)
Mà \(\frac{1}{65}+\frac{1}{64}-\frac{1}{63}+\frac{1}{62}\ne0\)
\(\Rightarrow x+66=0\)
\(\Rightarrow x=0-66=-66\)
Auto làm nốt câu b
a, Cộng cả 2 vế với 2
Ta có \(\frac{x+1}{64}+\frac{x+2}{63}+2=\frac{x+3}{62}+\frac{x+4}{61}+2\)
\(\left(\frac{x+1}{64}+\frac{64}{64}\right)+\left(\frac{x+2}{63}+\frac{63}{63}\right)=\left(\frac{x+3}{62}+\frac{62}{62}\right)+\left(\frac{x+4}{61}+\frac{61}{61}\right)\)
=> \(\frac{x+65}{64}+\frac{x+65}{63}=\frac{x+65}{62}+\frac{x+65}{61}\)\(\)
=> \(\frac{x+65}{64}+\frac{x+65}{63}-\frac{x+65}{62}-\frac{x+65}{61}=0\)
=> \(\left(x+65\right)\left(\frac{1}{64}+\frac{1}{63}-\frac{1}{62}-\frac{1}{61}\right)=0\)
Do \(\frac{1}{64}+\frac{1}{63}-\frac{1}{62}-\frac{1}{61}\ne0\)=> \(x+65=0\)
=> \(x=-65\)
b , Lm tương tự như Câu a
Chúc bn hok tốt
áp dụng \(\frac{a}{b}< 1\Rightarrow\frac{a+m}{b+m}< 1\left(m\in N\right)\)
Ta có: \(A=\frac{20^{102}+1}{20^{101}+1}< \frac{20^{102}+1+19}{20^{101}+1+19}=\frac{20.\left(20^{101}+1\right)}{20.\left(20^{100}+1\right)}=\frac{20^{101}+1}{20^{100}+1}\)
\(\Rightarrow A< B\)
\(\frac{20^{101}-1}{20^{102}-1}>\frac{20^{101}-20}{20^{102}-20}=\frac{20.\left(20^{100}-1\right)}{20.\left(20^{101}-1\right)}=\frac{20^{100}-1}{20^{101}-1}\)
\(\Rightarrow\frac{20^{101}-1}{20^{102}-1}>\frac{20^{100}-1}{20^{101}-1}\)
