a) \(\dfrac{-5}{9}-\dfrac{-5}{12}=\dfrac{-5}{9}+\dfrac{5}{12}=\dfrac{-20}{36}+\dfrac{15}{36}=-\dfrac{5}{36}\)

b) \(\dfrac{-5}{12}:\dfrac{15}{4}=\dfrac{-5}{12}\times\dfrac{4}{15}=\dfrac{-1}{9}\)

c) \(\dfrac{1}{13}\cdot\dfrac{8}{13}+\dfrac{5}{13}\cdot\dfrac{1}{13}-\dfrac{14}{13}=\dfrac{1}{13}\cdot\left(\dfrac{8}{13}+\dfrac{5}{13}\right)-\dfrac{14}{13}=\dfrac{1}{13}\cdot1-\dfrac{14}{13}=\dfrac{1}{13}-\dfrac{14}{13}=-1\)

a)=--5/36

b)=-1/9

c) =-1 

cách làm như trên

D

D

Đáp án\(\Rightarrow D\)

\(a,\dfrac{13}{14}\cdot\dfrac{-7}{8}+\dfrac{-3}{2}\)

\(=-\dfrac{13}{16}+\dfrac{-3}{2}\)

\(=-\dfrac{13}{16}+\dfrac{-24}{16}\)

\(=-\dfrac{37}{16}\)

\(b,\dfrac{5}{17}+\dfrac{-15}{34}\cdot\dfrac{2}{5}\)

\(=\dfrac{5}{17}+\dfrac{-3}{17}\)

\(=\dfrac{2}{17}\)

\(c,\dfrac{1}{5}:\dfrac{1}{10}-\dfrac{1}{3}\cdot\left(\dfrac{6}{5}-\dfrac{2}{4}\right)\)

\(=2-\dfrac{1}{3}\cdot\dfrac{7}{10}\)

\(=2-\dfrac{7}{30}\)

\(=\dfrac{53}{30}\)

\(d,\dfrac{-3}{4}:\left(\dfrac{12}{-5}-\dfrac{-7}{10}\right)\)

\(=\dfrac{-3}{4}:\dfrac{-17}{10}\)

\(=\dfrac{15}{34}\)

a: =4/5+1/5+2/3+1/3=1+1=2

b: =17/12+7/12+29/7-8/7=3+2=5

c: =3/5+2/5+16/7-1/7-1/7

=1+2=3

d: =2/5+3/5+2/3+1/3+7/4+1/4

=1+1+2

=4

\(\dfrac{4}{5}+\dfrac{2}{3}+\dfrac{1}{5}+\dfrac{1}{3}\)

\(=\left(\dfrac{4}{5}+\dfrac{1}{5}\right)+\left(\dfrac{2}{3}+\dfrac{1}{3}\right)\)

\(=\dfrac{5}{5}+\dfrac{3}{3}\)

\(=1+1\)

\(=2\)

============

\(\dfrac{17}{12}+\dfrac{29}{7}-\dfrac{8}{7}+\dfrac{7}{12}\)

\(=\left(\dfrac{17}{12}+\dfrac{7}{12}\right)+\left(\dfrac{29}{7}-\dfrac{8}{7}\right)\)

\(=\dfrac{24}{12}+\dfrac{21}{7}\)

\(=2+3\)

\(=5\)

====================

\(\dfrac{9}{15}+\dfrac{16}{7}+\dfrac{2}{5}-\dfrac{1}{7}-\dfrac{2}{14}\)

\(=\dfrac{9}{15}+\dfrac{16}{7}+\dfrac{6}{15}-\dfrac{1}{7}-\dfrac{1}{7}\)

\(=\left(\dfrac{9}{15}+\dfrac{6}{15}\right)+\left(\dfrac{16}{7}-\dfrac{1}{7}-\dfrac{1}{7}\right)\)

\(=\dfrac{15}{15}+\dfrac{14}{7}\)

\(=1+2\)

\(=3\)

===============

\(\dfrac{2}{5}+\dfrac{6}{9}+\dfrac{7}{4}+\dfrac{3}{5}+\dfrac{1}{3}+\dfrac{1}{4}\)

\(=\dfrac{2}{5}+\dfrac{2}{3}+\dfrac{7}{4}+\dfrac{3}{5}+\dfrac{1}{3}+\dfrac{1}{4}\)

\(=\left(\dfrac{2}{5}+\dfrac{3}{5}\right)+\left(\dfrac{2}{3}+\dfrac{1}{3}\right)+\left(\dfrac{7}{4}+\dfrac{1}{4}\right)\)

\(=\dfrac{5}{5}+\dfrac{3}{3}+\dfrac{8}{4}\)

\(=1+1+2\)

\(=4\)

a) \(\dfrac{1}{3}+\dfrac{3}{8}-\dfrac{7}{12}\)

\(=\dfrac{17}{24}-\dfrac{7}{12}\)

\(=\dfrac{1}{8}\)

b) \(\dfrac{-3}{14}+\dfrac{5}{8}-\dfrac{1}{2}\)

\(=\dfrac{23}{56}-\dfrac{1}{2}\)

\(=\dfrac{-5}{56}\)

c) \(\dfrac{1}{4}-\dfrac{2}{3}-\dfrac{11}{18}\)

\(=\dfrac{-5}{12}-\dfrac{11}{18}\)

\(=\dfrac{-37}{36}\)

d) \(\dfrac{1}{4}+\dfrac{5}{12}-\dfrac{1}{13}-\dfrac{7}{8}\)

\(=\dfrac{2}{3}-\dfrac{1}{13}-\dfrac{7}{8}\)

\(=\dfrac{23}{39}-\dfrac{7}{8}\)

\(=\dfrac{-89}{312}\)

a,4/5+1/6
=29/30

b,7/12+2-1/4
=31/12-1/4
=7/3

ĐKXĐ: x\(\ne\)4

\(\Leftrightarrow\dfrac{14}{3\left(x-4\right)}-\dfrac{x+2}{x-4}=\dfrac{3}{2\left(4-x\right)}-\dfrac{5}{6}\)

\(\Leftrightarrow\dfrac{14}{3\left(x-4\right)}-\dfrac{x+2}{x-4}+\dfrac{3}{2\left(x-4\right)}=-\dfrac{5}{6}\)

\(\Rightarrow14\cdot2-6\cdot\left(x+2\right)+3\cdot3=-5\left(x-4\right)\)

\(\Leftrightarrow28-6x-12+9=-5x+20\)

\(\Leftrightarrow25-6x=-5x+20\Leftrightarrow-6x+5x=20-25\Leftrightarrow-x=-5\Leftrightarrow x=5\left(TM\right)\)Vậy...

B=14:(\(\dfrac{35}{24}\))+14.\(\dfrac{1}{4}.\dfrac{2}{3}\)

B=14.\(\dfrac{24}{35}+14.\dfrac{1}{4}.\dfrac{2}{3}\)

B=14(\(\dfrac{24}{35}+\dfrac{1}{6}\))

B=14.\(\)\(\dfrac{179}{210}\)

B=\(\dfrac{179}{15}\)

`7 xx 3/14 -1/14`

`= 21/14 -1/14`

`= 20/14`

`=10/7`

__

`3/2 + 7/4 xx 2/5`

`= 3/2 + 14/20`

`= 3/2 + 7/10`

`= 15/10 +7/10`

`= 23/10`

__

`9/8 : 3 + 7/3 : 3`

`= 9/8 xx 1/3 + 7/3 xx 1/3`

`=1/3 xx ( 9/8 + 7/3)`

`= 1/3 xx 83/24`

`= 83/72`

__

`2 : 3/4 - 5/8 xx 4/3`

`= 2 xx 4/3 - 5/8 xx 4/3`

`= 4/3 xx ( 2-5/8)`

`= 4/3 xx ( 16/8 -5/8)`

`= 4/3 xx 11/8`

`= 44/24`

`=11/6`

` @ \color{Red}{sushiteam}`

=(2/7+5/7)+(3/11-6/11)+1/4

=5/4-3/11

=55/44-12/44=43/44