13/21<9/11

6/17<9/25

7/12>11/-18

tk mk nha mk đang âm điểm

chúc các bn hok tốt ^-^

thank you very much

a, vì 5/7<1<15/12

nên 5/7<15/12

b,17/21<17/19

\(\frac{5}{7}\)<\(\frac{15}{12}\)

\(\frac{17}{21}\)<\(\frac{17}{19}\)

a) ta thấy 5x12=5x3x4

còn 7x15=7x3x5

suy ra 5/7 nhỏ hơn

b) 21>19 nên 17/21 lớn hơn

a) \(\frac{34}{13}=2\frac{8}{13}\)

Vì 2 > 1 nên \(2\frac{8}{13}>1\frac{7}{9}\)

hay \(\frac{34}{13}>1\frac{7}{9}\)

b) \(\frac{7}{9}=1-\frac{2}{9}\)

\(\frac{13}{15}=1-\frac{2}{15}\)

Vì \(\frac{2}{9}>\frac{2}{15}\) nên \(\frac{7}{9}< \frac{13}{15}\)

a) Ta có:

\(1\frac{7}{9}=\frac{16}{9}=\frac{208}{117}\) 

\(\frac{34}{13}=\frac{306}{117}\)

Vì \(306>208\)

\(\Rightarrow\frac{306}{117}>\frac{208}{117}\)

\(\Rightarrow\frac{34}{13}>1\frac{7}{9}\)

b) Ta có:

\(\frac{7}{9}=\frac{35}{45}\)

\(\frac{13}{15}=\frac{39}{45}\)

Vì \(39>35\)

\(\Rightarrow\frac{39}{45}>\frac{35}{45}\)

\(\Rightarrow\frac{13}{15}>\frac{7}{9}\)

\(A=\frac{15}{34}+\frac{7}{21}+\frac{9}{34}-1\frac{15}{17}+\frac{2}{3}\)

   \(=\frac{12}{17}+\frac{1}{3}-\frac{32}{17}+\frac{2}{3}\)

   \(=-\frac{20}{17}+\frac{1}{3}+\frac{2}{3}\)

   \(=-\frac{20}{17}+1\)

   \(=-\frac{3}{17}\)

\(B=16\frac{2}{7}:\left(-\frac{3}{5}\right)-28\frac{2}{7}:\left(-\frac{3}{5}\right)\)

   \(=\left(\frac{114}{7}-\frac{198}{7}\right):\left(-\frac{3}{5}\right)\)

   \(=\left(-12\right):\left(-\frac{3}{5}\right)\)

   \(=20\)

A\(=\frac{15}{34}+\frac{7}{21}+\frac{9}{34}-1\frac{15}{17}+\frac{2}{3}\)

\(=\left(\frac{15}{34}+\frac{9}{34}\right)+\left(\frac{7}{21}+\frac{2}{3}\right)-1\frac{15}{17}\)

\(=\left(\frac{14}{17}-\frac{15}{17}\right)+1-1\)

\(=-\frac{1}{17}\)

\(B=16\frac{2}{7}:\left(-\frac{3}{5}\right)-28\frac{2}{7}:\left(-\frac{3}{5}\right)\)

\(B=-\frac{3}{5}.\left(16\frac{2}{7}-28\frac{2}{7}\right)\)

\(B=-\frac{3}{5}.\left(-12\right)\)

\(B=\frac{36}{5}\)

Hoctot

A=\(\frac{15}{34}\)+ \(\frac{7}{21}\)+  \(\frac{9}{34}\)- 1\(\frac{15}{17}\)+ \(\frac{2}{3}\)

   = ( \(\frac{15}{34}\)+ \(\frac{9}{34}\)) + ( \(\frac{7}{21}\)+ \(\frac{2}{3}\)) - \(\frac{32}{17}\)

  =  \(\frac{24}{34}\)+ ( \(\frac{7}{21}\)+ \(\frac{14}{21}\)) - \(\frac{32}{17}\)

  =\(\frac{12}{17}\)+ \(\frac{21}{21}\)- \(\frac{32}{17}\)

  = ( \(\frac{12}{17}\) - \(\frac{32}{17}\)) +1

  =\(\frac{-20}{17}\)+ \(\frac{17}{17}\)

  = \(\frac{-3}{17}\)

A. \(\frac{3}{4}\) x \(\frac{8}{9}\)x \(\frac{15}{16}\)x .... x \(\frac{899}{900}\)

= \(\frac{1.3}{2^2}\) x \(\frac{2.4}{3^3}\)x \(\frac{3.5}{4^2}\)x ... x \(\frac{29.31}{30^2}\)

= \(\left(\frac{1.2.3...29}{2.3.4...30}\right).\left(\frac{3.4.5...31}{2.3.4...30}\right)\)

= \(\frac{1}{30}.\frac{31}{2}\)= \(\frac{31}{60}\)

B. 

\(\frac{1}{3}+\frac{3}{8}-\frac{7}{12}=\frac{8}{24}+\frac{9}{24}-\frac{14}{24}=\frac{8+9-14}{24}=\frac{3}{24}=\frac{1}{8}\)

a)      Ta có: \(2 >  - 5\) nên \(\frac{2}{9} > \frac{{ - 5}}{9}\)hay \(\frac{2}{9} >  - \frac{5}{9}\).

b)      Ta có:

i) \(0 >  - 0,5\) nên  \({0^o}C > - 0,{5^o}C;\)

ii) Do \(12 > 7\) nên \( - 12 <  - 7\). Do đó, \( - {12^o}C < - {7^o}C\).

2.  a) \(3^{200}=\left(3^2\right)^{100}=9^{100}\)

          \(2^{300}=\left(2^3\right)^{100}=8^{100}\)

Vì \(9^{100}>8^{100}\Rightarrow3^{200}>2^{300}\)

b) \(71^{50}=\left(71^2\right)^{25}=5041^{25}\)

     \(37^{75}=\left(3^3\right)^{25}=27^{25}\)

Vì \(5041^{25}>27^{25}\Rightarrow71^{50}>37^{75}\)

c) \(\frac{201201}{202202}=\frac{201201:1001}{202202:1001}=\frac{201}{202}\)

      \(\frac{201201201}{202202202}=\frac{201201201:1001001}{202202202:1001001}=\frac{201}{202}\)

Vì \(\frac{201}{202}=\frac{201}{202}\Rightarrow\frac{201201}{202202}=\frac{201201201}{202202202}\)

Gyvyghghgbhg

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a) Ta có:

\(\frac{4}{9}< 1;\frac{5}{4}>1\)

Vì \(\frac{4}{9}< 1\)mà \(\frac{5}{4}>1\)nên \(\frac{4}{9}< \frac{5}{4}\)

Tương tự với \(\frac{2}{7}\) và \(\frac{7}{2}\)

A) 4/9 và 5/4

Ta có : Vì 4/9 < 1 ; 5/4 > 1

nên 4/9 < 5/4

2/7 và 7/2

Ta có : 2/7 < 1 ; 7/2 > 1

nên 2/7 < 7/2

nha bn