\(A=\dfrac{5}{11}.\dfrac{5}{7}+\dfrac{5}{11}.\dfrac{2}{7}+\dfrac{6}{11}=\dfrac{5}{11}\left(\dfrac{5}{7}+\dfrac{2}{7}\right)+\dfrac{6}{11}=\dfrac{5}{11}.1+\dfrac{6}{11}=\dfrac{5}{11}+\dfrac{6}{11}=\dfrac{11}{11}=1\)

\(B=\dfrac{3}{13}.\dfrac{6}{11}+\dfrac{3}{13}.\dfrac{9}{11}-\dfrac{3}{13}.\dfrac{4}{11}=\dfrac{3}{13}\left(\dfrac{6}{11}+\dfrac{9}{11}-\dfrac{4}{11}\right)=\dfrac{3}{13}.1=\dfrac{3}{13}\)

\(C=\left(\dfrac{12}{16}-\dfrac{31}{22}+\dfrac{14}{91}\right)\left(\dfrac{1}{2}-\dfrac{1}{3}-\dfrac{1}{6}\right)=\left(\dfrac{12}{16}-\dfrac{31}{22}+\dfrac{14}{91}\right)\left(\dfrac{3}{6}-\dfrac{2}{6}-\dfrac{1}{6}\right)=\left(\dfrac{12}{16}-\dfrac{31}{22}+\dfrac{14}{91}\right).0=0\)

-3/11.(-22)/66.121/15

=(-3).(-22).121

 11.66.15

=11

15

3/7.2/5.7/3.20.19/72

=3.2.7.20.19

7.5.3.72

=76

16

6/7.8/13+6/13.9/7-3/13.6/7

=6/7.8/13+6/7.9/13-3/13.6/7

=6/7.(8/13+9/13-3/13)

=6/7.14/13

=12/13

-1/4.152/11+68/4.(-1)/11

=152/4.(-1)/11+68/4.(-1)/11

=(-1)/11.(152/4+68/4)

=(-1)/11.220/4

=-110/22

-5/7.2/11+(-5)/7.9/11+12/7

=-5/7.2/11+-5/7.9/11+12/7

=-5/7.(2/11+9/11)+12/7

=-5/7.1+12/7

=(-5)/7+12/7

=7/7

=1

146/13-(18/7+68/13)

=146/13-18/7-68/13

=(146/13-68/13)-18/7

=78/13-18/7

=6-18/7

=42/7-18/7

=24/7

a) 5

b) 11/6

A=\(\frac{6}{19}\). \(\frac{-7}{11}\)+\(\frac{6}{19}\).\(\frac{-4}{11}\)+\(\frac{-13}{19}\)

  =\(\frac{6}{19}\).(\(\frac{-7}{11}\)+\(\frac{-4}{11}\))+\(\frac{-13}{19}\)

 =\(\frac{6}{19}\).\(\frac{-11}{11}\)+\(\frac{-13}{19}\)

  =\(\frac{6}{19}\).-1 +\(\frac{-13}{19}\)

=\(\frac{-6}{19}\)+\(\frac{-13}{19}\)

=\(\frac{-19}{19}\)

+1

=1  nhầm

Theo bài ra, ta chia thành các nhóm như sau:

1+(2-3-4+5)+(6-7-8+9)+.......+(298-299-300+301)+302 = 1+0+0+0+0+.......+0+302 = 1+302=303

                  Đáp số: 303

D/s303

\(\begin{array}{l}B = \left( {\frac{{ - 3}}{{13}}} \right) + \frac{{16}}{{23}} + \left( {\frac{{ - 10}}{{13}}} \right) + \frac{5}{{11}} + \frac{7}{{23}}\\ = \left[ {\left( {\frac{{ - 3}}{{13}}} \right) + \left( {\frac{{ - 10}}{{13}}} \right)} \right] + \left[ {\frac{{16}}{{23}} + \frac{7}{{23}}} \right] + \frac{5}{{11}}\\ =  - 1 + 1 + \frac{5}{{11}}\\ = \frac{5}{{11}}\end{array}\)

`B= ( (-3)/13 + (-10)/13) + (16/23 + 7/23 ) +5/11`

`B= -13/13 + 23/23 +5/11`

`B=-1+1+5/11`

`B=0+5/11`

`B=5/11`

 k cho mk nha !

Gợi ý: Sử dụng tính chất phân phối của phép nhân đối với phép cộng để nhóm thừa số chung ra ngoài.

A =\(\frac{7}{19}.\frac{8}{11}+\frac{7}{19}.\frac{3}{11}+\frac{12}{19}\)

A = \(\frac{7}{19}.\left(\frac{8}{11}+\frac{3}{11}\right)\)+ \(\frac{12}{19}\)

A = \(\frac{7}{19}.1+\frac{12}{19}\)

A = \(\frac{7}{19}+\frac{12}{19}\)

A = 1

--------

B = \(\frac{5}{9}.\frac{7}{13}+\frac{5}{9}.\frac{9}{13}-\frac{5}{9}.\frac{3}{13}\)

B = \(\frac{5}{9}.\left(\frac{7}{13}+\frac{9}{13}-\frac{3}{13}\right)\)

B = \(\frac{5}{9}.1\)

B = \(\frac{5}{9}\)

-------

C = \(\left(\frac{67}{111}+\frac{2}{33}-\frac{15}{117}\right).\left(\frac{1}{3}-\frac{1}{4}-\frac{1}{12}\right)\)

C = \(\left(\frac{67}{111}+\frac{2}{33}-\frac{15}{117}\right).\left(\frac{4}{12}-\frac{3}{12}-\frac{1}{12}\right)\)

C = \(\left(\frac{67}{111}+\frac{2}{33}-\frac{15}{117}\right).0\)

C = 0

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