đề là j

Tìm x :

\(\left(\dfrac{2}{3}x-\dfrac{4}{9}\right).\left(\dfrac{1}{2}+\dfrac{3}{7}:x\right)=0\)

\(\Rightarrow\left[{}\begin{matrix}\left(\dfrac{2}{3}x-\dfrac{4}{9}\right)=0\\\left(\dfrac{1}{2}+\dfrac{3}{7}:x\right)=0\end{matrix}\right.\) \(\Rightarrow\left[{}\begin{matrix}\dfrac{2}{3}x=\dfrac{4}{9}\\\dfrac{3}{7}:x=-\dfrac{1}{2}\end{matrix}\right.\Rightarrow\left[{}\begin{matrix}x=\dfrac{2}{3}\\x=-\dfrac{6}{7}\end{matrix}\right.\)

Vậy.....

Tính :

\(\dfrac{1313}{1515}+\left(-\dfrac{1011}{5055}\right)=\dfrac{13}{15}-\dfrac{1}{5}=\dfrac{2}{3}\)

không biết làm thì cứ qui đồng lên

phần b thì rút gọn đi đã

\(\left(\frac{1313}{1414}+\frac{10}{160}\right)-\left(\frac{130}{140}-\frac{1515}{1616}\right)\)

\(=\left(\frac{13}{14}+\frac{1}{16}\right)-\left(\frac{13}{14}-\frac{15}{16}\right)\)

\(=\frac{13}{14}+\frac{1}{16}-\frac{13}{14}+\frac{15}{16}\)

\(=\left(\frac{13}{14}-\frac{13}{14}\right)+\left(\frac{1}{16}+\frac{15}{16}\right)\)

\(=0+1\)

\(=1\)

Có (\(\frac{1313}{1414}\)+\(\frac{10}{160}\)) - (\(\frac{130}{140}\)-\(\frac{1515}{1616}\))

=\(\frac{13}{14}\)+\(\frac{1}{16}\)-\(\frac{13}{14}\)+\(\frac{15}{16}\)

=(\(\frac{13}{14}-\frac{13}{14}\)) + (\(\frac{1}{16}+\frac{15}{16}\))

=0+1=1

a) 123/127 = 123123/127127

Ta có 123123/127127 = 123 x 1001/127 x 1001

                              <=> 123123/ 127127 = 123 /127

Vậy 123/127 = 123123 /127127

b) 13/15 = 1313/1515 = 131313/151515

- Ta có 1313/1515 = 13 x 101 / 15 x 101 

                         <=> 1313/1515 = 13/15

- ta cũng có : 131313/151515 = 13 x 10101 / 15 x10101

                                          <=> 131313/151515 = 13/15 

Vậy 13/15 = 1313/1515 = 131313 /151515

Chúc bạn học tốt <3

123/127=123123/127127=123 x 1001/127 x 1001=123/127

13/15=1313/1515=13 x 101/15 x 101=13 x 10101/15 x 10101=13/15

ung ho nhe

\(\frac{123}{127}=\frac{123123}{127127}\Rightarrow\frac{123}{127}=\frac{123.1001}{127.1001}\Rightarrow\frac{123}{127}=\frac{123}{127}\Rightarrow\frac{123}{127}=\frac{123123}{127127}\)

\(\frac{13}{15}=\frac{1313}{1515}=\frac{131313}{151515}\Rightarrow\frac{13}{15}=\frac{13.101}{15.101}=\frac{13.10101}{15.10101}\Rightarrow\frac{13}{15}=\frac{13}{15}=\frac{13}{15}\Rightarrow\frac{13}{15}=\frac{1313}{1515}=\frac{131313}{151515}\)

Ai làm đúng và nhanh nhất mk k cho

cái thứ hai lớn hơn

Ta có : \(\frac{1212+1313+1414+1515+1616}{1717+1818+1919+2020+2121}=\frac{12+13+14+15+16}{17+18+19+20+21}=\frac{28\cdot\frac{5}{2}}{38\cdot\frac{5}{2}}=\frac{14}{19}\)

Dễ thấy \(\frac{111111}{666665}< \frac{1}{2}\) ( do 111111 < 666665/2 ) và \(\frac{14}{19}>\frac{1}{2}\) ( do 14 > 19/2 )

Vậy \(\frac{111111}{666665}< \frac{1212+1313+1414+1515+1616}{1717+1818+1919+2020+2121}\)

\(\frac{1010+1111+1212+1313+1414+1515+1616+1717}{2020+2121+2222+2323+2424+2525+2626+2727}\)

\(=\frac{101.10+101.11+...+101.17}{101.20+101.21+...+101.27}\)

\(=\frac{101.\left(10+11+...+17\right)}{101.\left(20+21+...+27\right)}\)

\(=\frac{108}{188}\)

\(=\frac{27}{47}\)

\(2>\left(\frac{1}{6}+\frac{2}{15}+\frac{3}{40}+\frac{4}{96}\right)\cdot5.y>\frac{5}{6}\)

\(\Rightarrow2>\left(\frac{1}{6}+\frac{2}{15}+\frac{3}{40}+\frac{1}{24}\right):5.y>\frac{5}{6}\)

\(\Rightarrow2>\left(\frac{20}{120}+\frac{16}{120}+\frac{9}{120}+\frac{5}{120}\right):5.y>\frac{5}{6}\)

\(\Rightarrow2>\frac{5}{12}:5.y>\frac{5}{6}\)

\(\Rightarrow2>\frac{1}{12}.y>\frac{5}{6}\)

Đặt :\(\frac{1}{12}.y=2\Rightarrow y=2:\frac{1}{12}=24\)

\(\frac{1}{12}.y=\frac{5}{6}\Rightarrow y=\frac{5}{6}:\frac{1}{12}=10\)

\(\Rightarrow24>y>10\)

\(\Rightarrow y\in\left\{11;12;...;23\right\}\)

ko biết

I am sorry

Kb nhé

**** cho mk coi nào 

đúng hay sai cũng nên ủng hô mik chứ

Một tuần rồi mà có 1****

Ta thấy : 1313/2121 = 1313 : 101 = 13   , 1515 : 101 = 15   , 424242 : 30303 = 14 , 
                                      2121 : 101 = 21    1313 : 101    13     151515 : 30303  5  
 Vậy 13 x 15 x 14  =  14
          21 x 13 x 15 =  21
 Bạn k cho mình đi mình nhanh nhất với lại đúng nữa !!!