a: =35/17-18/17-9/5+4/5

=1-1=0

b: =-7/19(3/17+8/11-1)

=7/19*18/187=126/3553

c: =26/15-11/15-17/3-6/13

=1-6/13-17/3

=7/13-17/3=-200/39

\(A=\frac{2}{7}+\frac{-3}{8}+\frac{11}{7}+\frac{1}{3}+\frac{1}{7}+\frac{5}{-8}\)

\(A=\left(\frac{2}{7}+\frac{11}{7}+\frac{1}{7}\right)+\left(\frac{-3}{8}+\frac{5}{-8}\right)+\frac{1}{3}\)

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

\(A=\frac{4}{3}\)

\(B=\frac{3}{17}+\frac{-5}{13}+\frac{-18}{35}+\frac{14}{17}+17\)

\(B=\left(\frac{3}{17}+\frac{14}{17}\right)+\frac{-5}{13}+\frac{-18}{35}+17\)

\(B=1+\frac{-5}{13}+\frac{-18}{35}+17\)

\(B=18+\frac{-5}{13}+\frac{-18}{35}\)

\(B=\frac{7781}{455}\)

A  =\(\frac{2}{5}\times\frac{4}{7}+\frac{3}{5}\times\frac{4}{7}\)  B = \(\frac{17}{13}\times\frac{12}{17}-\frac{4}{13}\times\frac{12}{17}\)   C = \(\frac{9}{14}:\frac{6}{7}+\frac{5}{14}:\frac{6}{7}\)  D =\(\frac{9}{12}:\frac{7}{9}\times\frac{12}{19}\)

=  \(\frac{4}{7}\times\left(\frac{2}{5}+\frac{3}{5}\right)\)              =\(\left(\frac{17}{13}-\frac{4}{13}\right)\times\frac{12}{17}\)                = \((\frac{9}{14}+\frac{5}{14}):\frac{6}{7}\)         = \(\frac{9}{12}\times\frac{9}{7}\times\frac{12}{19}\)

=\(\frac{4}{7}\times1\)                                     = \(1\times\frac{12}{17}\)                                       = \(1:\frac{6}{7}\)                               = \(\frac{9\times9\times12}{12\times7\times19}\)

=\(\frac{4}{7}\)                                              =  \(\frac{12}{17}\)                                                =\(\frac{7}{6}\)                                    = \(\frac{9\times9}{7\times19}=\frac{81}{133}\)

   -  

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a)14/13+(-1/13-19/20)=1/20 

b)-24/17-(-7/17-1/16)=-479/272

\(a,=\dfrac{14}{13}-\dfrac{1}{13}-\dfrac{19}{20}\\ =1-\dfrac{19}{20}=\dfrac{20}{20}-\dfrac{19}{20}\\ =\dfrac{1}{20}\\ b,=\dfrac{-24}{17}+\dfrac{7}{17}+\dfrac{1}{16}\\ =-1+\dfrac{1}{16}\\ =\dfrac{-16}{16}+\dfrac{1}{16}=\dfrac{-15}{16}\)

^{_{a)14/13+(-1/13-19/20)=1/20}}

^{_{b)-24/17-(-7/17-1/16)=-479/272}}

Cách hai:

A; \(\dfrac{17}{19}\) x \(\dfrac{12}{15}\) x \(\dfrac{19}{17}\)

= \(\dfrac{68}{95}\) x \(\dfrac{19}{17}\)

= \(\dfrac{4}{5}\)

Cách 1:

A. \(\dfrac{17}{19}\) x \(\dfrac{12}{15}\) x \(\dfrac{19}{17}\)

= (\(\dfrac{17}{19}\) x \(\dfrac{19}{17}\)) x \(\dfrac{12}{15}\)

= \(1\) x \(\dfrac{12}{15}\)

= \(\dfrac{4}{5}\)

B; Cách 1: (\(\dfrac{5}{7}\) + \(\dfrac{9}{7}\)) x \(\dfrac{21}{28}\)

                 =  2 x \(\dfrac{3}{4}\)

                 =   \(\dfrac{3}{2}\)

Cách 2:   (\(\dfrac{5}{7}+\dfrac{9}{7}\)) x \(\dfrac{21}{28}\) 

             =  \(\dfrac{5}{7}\) x \(\dfrac{21}{28}\) + \(\dfrac{9}{7}\) x \(\dfrac{21}{28}\)

             =   \(\dfrac{15}{28}\) + \(\dfrac{27}{28}\)

            = \(\dfrac{42}{28}\)

            = \(\dfrac{3}{2}\)

C1 :9/7 : 17/14 + 8/7 : 17/14

= (9/7 + 8/7) : 17/14

= 17/7 : 17/14

= 238/119

C2 : 9/7 : 17/14 + 8/7 : 17/14

= 9/7 x 14/17 + 8/7 x 14/17

= (9/7 + 8/7) x 14/17

= 17/7 x 14/17

= 238 /119

C1:(0,9 + 1,05) : 0,25

  = 1,95 : 0,25

= 7,8

C2 : (0,9 + 1,05) : 0,25

= 0,9 : 0,25 + 1,05 : 0,25

= 3,6 + 4,2

= 7,8

tự rút gọn nha

bài : 9/7 : 17/14 + 8/7 : 17/14 = 2 nha

\(-\dfrac{5}{14}:\dfrac{7}{17}-\dfrac{5}{14}:\dfrac{7}{11}-\dfrac{6}{7}=\dfrac{5}{14}:\left(-\dfrac{7}{17}\right)-\dfrac{5}{14}:\dfrac{7}{11}-\dfrac{6}{7}\)

\(=\dfrac{5}{14}.\left(-\dfrac{17}{7}\right)-\dfrac{5}{14}.\dfrac{11}{7}-\dfrac{6}{7}=\dfrac{5}{14}.\left(-\dfrac{17}{7}-\dfrac{11}{7}\right)-\dfrac{6}{7}\)

\(=\dfrac{5}{14}.\left(-4\right)-\dfrac{6}{7}=-\dfrac{10}{7}-\dfrac{6}{7}=-\dfrac{16}{7}\)

\(-\dfrac{5}{14}\) hay \(\dfrac{5}{14}\) vậy