nhanh lên

a: \(=\dfrac{3}{22}\cdot22\cdot\dfrac{3}{11}=3\cdot\dfrac{3}{11}=\dfrac{9}{11}\)

b: \(=\dfrac{5}{6}\cdot\dfrac{2}{5}=\dfrac{1}{3}\)

c: \(=\dfrac{17}{21}\left(\dfrac{3}{5}+\dfrac{2}{5}\right)=\dfrac{17}{21}\)

a : = \(\dfrac{3}{22}\). 22 . \(\dfrac{3}{11}\) = 3 . \(\dfrac{3}{11}\) = \(\dfrac{9}{11}\)

b : = \(\dfrac{5}{6}\). \(\dfrac{2}{5}\) = \(\dfrac{1}{3}\)

c: = \(\dfrac{17}{21}\)(\(\dfrac{3}{5}\) + \(\dfrac{2}{5}\)   ) = \(\dfrac{17}{21}\)

Cách 1 : \(\dfrac{5}{7}\times\dfrac{3}{21}+\dfrac{2}{7}\times\dfrac{3}{21}=\dfrac{5}{49}+\dfrac{2}{49}=\dfrac{1}{7}\)

Cách 2 : \(\dfrac{5}{7}\times\dfrac{3}{21}+\dfrac{2}{7}\times\dfrac{3}{21}=\dfrac{3}{21}\times\left(\dfrac{5}{7}+\dfrac{2}{7}\right)=\dfrac{1}{7}\times1=\dfrac{1}{7}\)

a: Ta có: \(\left|\dfrac{2}{5}-x\right|+\dfrac{1}{2}=3.5\)

\(\Leftrightarrow\left|x-\dfrac{2}{5}\right|=3\)

\(\Leftrightarrow\left[{}\begin{matrix}x-\dfrac{2}{5}=3\\x-\dfrac{2}{5}=-3\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=\dfrac{17}{5}\\x=-\dfrac{13}{5}\end{matrix}\right.\)

b: Ta có: \(\dfrac{21}{5}+3:\left|\dfrac{x}{4}-\dfrac{2}{3}\right|=6\)

\(\Leftrightarrow3:\left|\dfrac{1}{4}x-\dfrac{2}{3}\right|=6-\dfrac{21}{5}=\dfrac{9}{5}\)

\(\Leftrightarrow\left|\dfrac{1}{4}x-\dfrac{2}{3}\right|=\dfrac{5}{3}\)

\(\Leftrightarrow\left[{}\begin{matrix}\dfrac{1}{4}x-\dfrac{2}{3}=\dfrac{5}{3}\\\dfrac{1}{4}x-\dfrac{2}{3}=-\dfrac{5}{3}\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}\dfrac{1}{4}x=\dfrac{7}{3}\\\dfrac{1}{4}x=-1\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=\dfrac{28}{3}\\x=-4\end{matrix}\right.\)

a: \(=\dfrac{3}{5}:\dfrac{7}{5}=\dfrac{3}{5}\cdot\dfrac{5}{7}=\dfrac{3}{7}\)

b: \(=\dfrac{9}{17}\left(\dfrac{8}{5}-\dfrac{3}{5}\right)+\dfrac{8}{17}\)

=9/17+8/17=1

c: =>x-3/10=7/15*1/5=7/75

=>x=7/75+3/10=59/150

\(\frac{3}{5}\times\frac{7}{21}+\frac{7}{21}\times\frac{2}{5}=\frac{7}{21}\times\left(\frac{3}{5}+\frac{2}{5}\right)=\frac{1}{3}\times\left(\frac{3}{5}+\frac{2}{5}\right)=\frac{1}{3}\times1=\frac{1}{3}\)

   Học tốt !

\(\frac{3}{5}\cdot\frac{7}{21}+\frac{7}{21}+\frac{2}{5}\)

\(=\frac{7}{21}\cdot(\frac{3}{5}+\frac{2}{5})\)

\(=\frac{7}{21}\cdot1=\frac{7}{21}=\frac{1}{3}\)

C1  \(\frac{3}{5}.\frac{7}{21}+\frac{7}{21}.\frac{2}{5}\)

\(=\frac{7}{21}\left(\frac{3}{5}+\frac{2}{5}\right)\)

\(=\frac{7}{21}.1\)

\(=\frac{7}{21}=\frac{1}{3}\)

C2   \(\frac{3}{5}.\frac{7}{21}+\frac{7}{21}.\frac{2}{5}\)

\(=\frac{3.7}{5.21}+\frac{7.2}{21.5}\)

\(=\frac{21}{105}+\frac{14}{105}\)

\(=\frac{35}{105}\)

\(=\frac{7}{21}=\frac{1}{3}\)

\(\frac{-8}{3}+\frac{-1}{3}\)=\(\frac{-9}{3}\)

=-3

\(\frac{-2}{7}+\frac{-1}{7}=\frac{-3}{7}< 0\)

Đề bài trở thành:-3<x<0

Vậy các số cần tìm là -2;-1

lát mình giải tiếp nha

Ý 2 quy đồng mẫu số là 168 rổi khử mẫu đi.Sau đó thì tự giải

Ý 3 quy đồng mẫu số là 120 rổi khử mẫu đi.Sau đó thì tự giải

=>Không rỗi hơi quy đồng mẫu lớn thế đâu

Cần chi tiết hum bẹn

a) = 76/35 ; 37/9

b) 143/40 ; 19/15

c) 2/3 ; 42/5

d) 21/4 ; 4/7 

a, 11/7 + 3/5

= \(\dfrac{11x5}{7x5}+\dfrac{3x7}{5x7}=\dfrac{55}{35}+\dfrac{21}{35}=\dfrac{76}{35}\)

4 + 1/9

= \(\dfrac{4}{1}+\dfrac{1}{9}=\dfrac{4x9}{1x9}+\dfrac{1x1}{9x1}=\dfrac{36}{9}+\dfrac{1}{9}=\dfrac{37}{9}\)

b, 21/5 - 5/8

= \(\dfrac{21x8}{5x8}-\dfrac{5x5}{8x5}=\dfrac{168}{40}-\dfrac{25}{40}=\dfrac{143}{40}\)

2 - 11/15

=\(\dfrac{2}{1}-\dfrac{11}{15}=\dfrac{30}{15}-\dfrac{11}{15}=\dfrac{19}{15}\)

MIK LÀM ĐC NGẦN ĐẤY THUI BẸN THÔNG CẢM

\(\dfrac{26}{81}+\dfrac{4}{27}=\dfrac{26+12}{81}=\dfrac{38}{81}\)

\(\dfrac{5}{64}+\dfrac{7}{8}=\dfrac{5+56}{64}=\dfrac{61}{64}\)

\(\dfrac{26}{81}+\dfrac{4}{27}=\dfrac{26}{81}+\dfrac{4\times3}{27\times3}=\dfrac{26}{81}+\dfrac{12}{81}=\dfrac{38}{81}\)

\(\dfrac{5}{64}+\dfrac{7}{8}=\dfrac{5}{64}+\dfrac{7\times8}{8\times8}=\dfrac{5}{64}+\dfrac{56}{64}=\dfrac{61}{64}\)