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b: \(\dfrac{7}{8}=\dfrac{7\cdot5}{8\cdot5}=\dfrac{35}{40};\dfrac{4}{5}=\dfrac{4\cdot8}{5\cdot8}=\dfrac{32}{40}\)

35>32

=>\(\dfrac{35}{40}>\dfrac{32}{40}\)

=>\(\dfrac{7}{8}>\dfrac{4}{5}\)

c: \(\dfrac{5}{8}=\dfrac{5\cdot2}{8\cdot2}=\dfrac{10}{16}>\dfrac{7}{16}\)

d: \(\dfrac{5}{16}=0,3125< 0,37\)

e: \(\dfrac{3}{5}=\dfrac{3\cdot7}{5\cdot7}=\dfrac{21}{35};\dfrac{5}{7}=\dfrac{5\cdot5}{7\cdot5}=\dfrac{25}{31}\)

21<25

=>\(\dfrac{21}{35}< \dfrac{25}{35}\)

=>\(\dfrac{3}{5}< \dfrac{5}{7}\)

f: \(\dfrac{6}{11}=0,\left(54\right)=0,5454...>0,54\)

g: \(\dfrac{4}{9}=\dfrac{4\cdot7}{9\cdot7}=\dfrac{28}{63};\dfrac{3}{7}=\dfrac{3\cdot9}{7\cdot9}=\dfrac{27}{63}\)

28>27

=>\(\dfrac{28}{63}>\dfrac{27}{63}\)

=>\(\dfrac{4}{9}>\dfrac{3}{7}\)

h: \(\dfrac{1}{9}=0,\left(1\right)=0,1111...< 0,114...\)

10 tháng 2 2018

xem trên mạng

25 tháng 6 2018

Xem trên mạng

\(A=\frac{3}{8^3}+\frac{7}{8^4}=\frac{3}{8^3}+\frac{3}{8^4}+\frac{4}{8^4}\)

\(B=\frac{7}{8^3}+\frac{3}{8^4}=\frac{3}{8^3}+\frac{3}{8^4}+\frac{4}{8^4}\)

\(A=\frac{3}{8^3}+\frac{3}{8^4}+\frac{4}{8^3}>B=\frac{3}{8^3}+\frac{3}{8^4}+\frac{4}{8^4}\)

vậy A>B

22 tháng 2 2017

A=(24+7)/8^4 =31/8^4 
B=(56+3)/8^4 = 59/8^4 
=> A<B

11 tháng 11 2020

what your name? I can't speak vietnamese

a) \(6.8^{x-1}+8^{x+1}=6.8^{19}+8^{21}\)

\(\Rightarrow x-1+x+1=19+21\)

\(=2x=40\)

\(\Rightarrow x=20\)

b) \(4.3^{x-1}+2.3^{x+2}=4.3^6+2.3^9\)

\(\Rightarrow x-1+x+2=6+9\)

\(\Rightarrow2x+1=15\)

\(\Rightarrow2x=14\)

\(\Rightarrow x=7\)

15 tháng 9 2017

\(A=\dfrac{4^{10}+8^4}{4^5+8^6}\)

\(A=\dfrac{2^{20}+2^{12}}{2^{10}+2^{18}}=\dfrac{\left(2^8+1\right).2^{12}}{\left(1+2^8\right).2^{10}}\)

\(=\dfrac{\left(256+1\right).2^2}{1+256}=\dfrac{257.2^2}{257}=2^2\)

\(B=\dfrac{1+3^4+3^8+3^{12}}{1+3^2+3^4+3^6+3^8+3^{10}+3^{12}+3^{14}}\)

\(=\dfrac{1+81+6561+3^{12}}{1+9+81+729+6561+59049+3^{12}+3^{14}}\)

\(=\dfrac{6643+3^{12}}{91+719+6561+59049+3^{12}+3^{14}}\)

\(=\dfrac{6643+3^{12}}{66430+3^{12}+3^{14}}\)

P/s : Nổi hứng lên thì lm chứ k bt đúng hay sai :V

6 tháng 10 2017

B sai bae nhs

\(2^x=8^3.8^{-10}.8^3=8^{-4}=2^{-12}\\ \Rightarrow x=-12\)

13 tháng 7 2015

 

\(\left|\frac{-2}{3}x+\frac{3}{8}\right|\left(-\frac{8}{5}\right)=\frac{-8}{15}\)

\(\left|\frac{-2}{3}x+\frac{3}{8}\right|=\frac{-8}{15}:\frac{-8}{15}\)

\(\left|\frac{-2}{3}x+\frac{3}{8}\right|=1\)

\(\Rightarrow-\frac{2}{3}x+\frac{3}{8}\in\left\{1;-1\right\}\)

\(\Rightarrow-\frac{2}{3}x\in\left\{\frac{5}{8};\frac{-11}{8}\right\}\)

\(\Rightarrow x\in\left\{\frac{-15}{16};\frac{33}{16}\right\}\)