làm hộ tớ  nhé

ngu the  xcuiegudg

sao chửi người ta ngu có khi còn ngu hơn người ta nữa ở đó mà lên giọng

Ta có : 1/4=1/2*2>1/2*3

            1/9=1/3*3>1/3*4

            ...

           1/100=1/10*10>1/10*11

=>A>1/2*3+1/3*4+...+1/10*11=1/2 - 1/3+1/3 - 1/4 +...+1/10 - 1/11

=1/2 - 1/11=9/22=54/132<65/132(bạn hình như viết sai đầu bài chứ cách này đúng mà!)

cảm ơn nha

\(=1\frac{364}{729}\)\(=1+\frac{1}{3}+\frac{1}{9}+\frac{1}{27}+\frac{1}{81}+\frac{1}{243}+\frac{1}{729}=1+\frac{243}{729}+\frac{81}{729}+\frac{27}{729}+\frac{9}{729}+\frac{3}{729}+\frac{1}{729}=1\frac{ }{ }\)

\(=1\frac{364}{729}\)

a=\(\frac{1}{2^2}+\frac{1}{3^2}+\frac{1}{4^2}+.....+\frac{1}{10^2}\)

a>\(\frac{1}{2.3}+\frac{1}{3.4}+\frac{1}{4.5}+.....+\frac{1}{10.11}\)

  =\(\frac{1}{2}-\frac{1}{11}\)

a) \(27^{64}:81^{20}=3^{192}:3^{80}=3^{112}\)

b) \(\left(\dfrac{1}{8}\right)^{20}:\left(\dfrac{1}{16}\right)^9=\left(\dfrac{1}{2}\right)^{60}:\left(\dfrac{1}{2}\right)^{36}=\left(\dfrac{1}{2}\right)^{24}\)

c) \(\dfrac{1}{3}:\dfrac{1}{5}-\dfrac{1}{6}=\dfrac{5}{3}-\dfrac{1}{6}=\dfrac{10}{6}-\dfrac{1}{6}=\dfrac{9}{6}=\dfrac{3}{2}\)

=81/81+27/81+9/81+3/81+1/81=121/81

1. Tinh:

a) 1 + 1 phần 3 + 1 phần 9 + 1 phần 27 + 1 phần 81 = 81/81 + 27/81 + 9/81 + 3/81 + 1/81 = 121/81

đặt \(S=1+\frac{1}{3}+\frac{1}{9}+\frac{1}{27}+\frac{1}{81}\)

\(=1+\frac{1}{3^1}+\frac{1}{3^2}+\frac{1}{3^3}+\frac{1}{3^4}\)

\(\Rightarrow3S=3+1+\frac{1}{3^1}+\frac{1}{3^2}+\frac{1}{3^3}\)

\(\Rightarrow3S-S=3-\frac{1}{3^4}\)

\(\Rightarrow2S=\frac{80}{81}\)

\(\Rightarrow S=\frac{\frac{80}{81}}{2}\)

\(=\frac{80}{162}\)

\(=\frac{40}{81}\)