bài 1: 

\(2\dfrac{3}{4}:1\dfrac{1}{3}=\dfrac{11}{4}:\dfrac{4}{3}=\dfrac{33}{16}\)

`4/7+4`

`=4/7+4/1`

`=4/7+28/7`

`=32/7`

__

`3+6/11`

`=33/11+6/11`

`=39/11`

__

`3-5/7`

`=3/1-5/7`

`=21/7-5/7`

`=16/7`

__

`21/9-2`

`=21/9-18/9`

`=3/9`

`=1/3`

__

`15/24+2`

`=15/24+48/24`

`=63/24`

`=21/16`

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`63/45-20/25`

`=63/45-4/5`

`=63/45-36/45`

`=27/45`

`=9/15`

__

`3/4-2/8`

`=3/4-1/4`

`=2/4`

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`6/7-5/8`

`=48/56-35/56`

`=13/56`

__

`37/45-5/9`

`=37/45-25/45`

`=12/45`

`=4/15`

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`46/39-11/13`

`=46/39-33/39`

`=13/39`

`=1/2`

__

`5/12+3/4+1/3`

`=5/12+9/12+4/12`

`=14/12+4/12`

`=18/12`

`=3/2`

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`1/2+3/7+11/14`

`=7/14+6/14+11/14`

`=13/14+11/14`

`=24/14`

`=12/7`

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`7/10-(1/5+1/4)`

`=7/10-(4/20+5/20)`

`=7/10-9/20`

`=14/20-9/20`

`=5/20`

`=1/4`

__

`15/4-2/3-3/4`

`=(15/4-3/4)-2/3`

`=12/4-2/3`

`=3-2/3`

`=9/3-2/3`

`=7/3`

4) \(\left(\dfrac{3}{7}\right)^2\cdot\left(-7\right)^4\)

\(=\left(\dfrac{3}{7}\right)^2\cdot\left[\left(-7\right)^2\right]^2\)

\(=\left(\dfrac{3}{7}\right)^2\cdot49^2\)

\(=\left(\dfrac{3}{7}\cdot49\right)^2\)

\(=\left(\dfrac{147}{7}\right)^2\)

\(=21^2\)

\(=441\)

5) \(\left(-11\right)^{12}\cdot\left(\dfrac{4}{11}\right)^6\)

\(=\left[\left(-11\right)^2\right]^6\cdot\left(\dfrac{4}{11}\right)^6\)

\(=121^6\cdot\left(\dfrac{4}{11}\right)^6\)

\(=\left(121\cdot\dfrac{4}{11}\right)^6\)

\(=44^6\)

6) \(6^8\cdot\left(\dfrac{5}{7}\right)^7\)

\(=6^8\cdot\dfrac{5^7}{6^7}\)

\(=\dfrac{6^8\cdot5^7}{6^7}\)

\(=6\cdot5^7\)

\(=469750\)

\(\left(\dfrac{3}{7}\right)^2\cdot\left(-7\right)^4=\dfrac{9}{49}\cdot49^2=9\cdot49=441\)

\(\left(-11\right)^{12}\cdot\left(\dfrac{4}{11}\right)^4=11^{12}\cdot\dfrac{4^4}{11^4}=11^8\cdot4^4=54875873536\) 

\(\left(-6\right)^8\cdot\left(\dfrac{5}{6}\right)^7=6^8\cdot\dfrac{5^7}{6^7}=6\cdot5^7=469750\)

\(A=\left(\dfrac{5}{12}.\dfrac{21}{15}\right):\dfrac{1}{4}\)

\(=\dfrac{7}{12}:\dfrac{1}{4}\)

\(=\dfrac{28}{12}=\dfrac{7}{3}\)

\(B=\left(\dfrac{2}{7}:\dfrac{5}{4}\right).\left(\dfrac{5}{8}:2\right)\)

\(=\dfrac{8}{35}.\left(\dfrac{5}{8}:2\right)\)

\(=\dfrac{8}{35}.\dfrac{5}{16}\)

\(=\dfrac{1}{14}\)

\(C=\left(\dfrac{11}{15}.\dfrac{35}{44}\right).\left(\dfrac{1}{7}.\dfrac{4}{13}\right)\)

\(=\dfrac{7}{12}.\left(\dfrac{1}{7}.\dfrac{4}{13}\right)\)

\(=\dfrac{7}{12}.\left(\dfrac{1}{7}.\dfrac{4}{13}\right)\)

\(=\dfrac{7}{12}.\dfrac{4}{91}\)

\(=\dfrac{1}{39}\)

\(D=\left(\dfrac{7}{20}+\dfrac{11}{15}-\dfrac{15}{12}\right):\left(\dfrac{11}{20}-\dfrac{26}{45}\right)\)

\(=\left(\dfrac{13}{12}-\dfrac{15}{12}\right):\left(\dfrac{11}{20}-\dfrac{26}{45}\right)\)

\(=\dfrac{-1}{6}:\left(\dfrac{11}{20}-\dfrac{26}{45}\right)\)

\(=\dfrac{-1}{6}:\dfrac{-1}{36}\)

\(=6\)

Bài 1:

a: \(x=\dfrac{2}{3}:\dfrac{3}{5}=\dfrac{2}{3}\cdot\dfrac{5}{3}=\dfrac{10}{9}\)

b: \(x=\dfrac{17}{8}:\dfrac{7}{17}=\dfrac{17}{8}\cdot\dfrac{17}{7}=\dfrac{289}{56}\)

c: \(x=-\dfrac{3}{4}:\dfrac{7}{12}=\dfrac{-3}{4}\cdot\dfrac{12}{7}=\dfrac{-63}{28}=-\dfrac{9}{4}\)

d: \(\Leftrightarrow x\cdot\dfrac{1}{6}=\dfrac{3}{8}-\dfrac{1}{4}=\dfrac{1}{4}\)

hay \(x=\dfrac{1}{4}:\dfrac{1}{6}=\dfrac{3}{2}\)

e: \(\Leftrightarrow\dfrac{1}{2}:x=-4-\dfrac{1}{3}=-\dfrac{17}{3}\)

hay \(x=-\dfrac{1}{2}:\dfrac{17}{3}=\dfrac{-3}{34}\)

dad

1: 243^5=(3^5)^5=3^25

3*27^8=3*(3^3)^8=3^25

=>243^5=3*27^8

6: 125^5=(5^3)^5=5^15

25^7=(5^2)^7=5^14

=>125^5>25^7(15>14)

5: 78^12-78^11=78^11(78-1)=78^11*77

78^11-78^10=78^10*77

mà 11>10

nên 78^12-78^11>78^11-78^10

Ghi đầy đủ nha

bn có thể ghi rõ ràng đc ko?

a)\(-\dfrac{3}{7}+\dfrac{5}{13}+\dfrac{3}{7}\) 

=\(\left(-\dfrac{3}{7}+\dfrac{3}{7}\right)+\dfrac{5}{13}\) 

=\(0+\dfrac{5}{13}\) 

=\(\dfrac{5}{13}\)