A = (26/15 - 11/15) + (-7/13 + -6/13)

= 15/15 + -13/13

= 1 + (-1)

=0

a/\(\dfrac{26}{15}+-\dfrac{7}{13}+-\dfrac{6}{13}-\dfrac{11}{15}\)
\(=\left(\dfrac{26}{15}-\dfrac{11}{15}\right)-\left(\dfrac{7}{13}+\dfrac{6}{13}\right)\)
\(=1-1\)
\(=0\)
b/Sửa đề:
\(-\dfrac{3}{4}\cdot\dfrac{4}{13}+-\dfrac{3}{4}\cdot\dfrac{9}{13}+\dfrac{3}{4}\)
\(=-\dfrac{3}{4}\cdot\left(\dfrac{4}{13}+\dfrac{9}{13}\right)+\dfrac{3}{4}\)
\(=-\dfrac{3}{4}\cdot1+\dfrac{3}{4}\)
\(=-\dfrac{3}{4}+\dfrac{3}{4}\)
\(=0\)

câu b ko tính nhanh được, nếu đề sai thì đã có bài của ctv rồi nhé

C

C

C NHA BẠN 

CHÚC BẠN HỌC TỐT ^^

= \(\frac{4}{13}.\left(\frac{5}{11}+\frac{6}{11}-1\right)=\frac{4}{13}.\left(\frac{11}{11}-1\right)=\frac{4}{13}.0=0\)

-20/221+-48/221+4/13

-68/221+4/13

-68/221+20/221

-48/221

\(1.\dfrac{-7}{18}+\dfrac{-5}{12}-\dfrac{-13}{18}\text{=}\left(\dfrac{-7}{18}-\dfrac{-13}{18}\right)+\dfrac{-5}{12}\text{=}\dfrac{1}{3}+\dfrac{-5}{12}\text{=}\dfrac{-1}{12}\)

\(2.\dfrac{-13}{17}+\dfrac{-13}{21}+\dfrac{-4}{17}\text{=}\left(\dfrac{-13}{17}+\dfrac{-4}{17}\right)+\dfrac{-13}{21}\text{=}-1+\dfrac{-13}{21}\text{=}\dfrac{-34}{21}\)

\(3.\dfrac{-13}{10}-\dfrac{-4}{13}+\dfrac{-11}{10}\text{=}\dfrac{-12}{5}-\dfrac{-4}{13}\text{=}\dfrac{-136}{65}\)

\(4.\dfrac{13}{17}\times\left(\dfrac{-4}{5}+\dfrac{-3}{4}\right)\text{=}\dfrac{13}{17}\times\dfrac{-31}{20}\text{=}\dfrac{-403}{340}\)

\(5.\left(\dfrac{-5}{12}\times\dfrac{-9}{20}\right)\times\dfrac{-7}{17}\text{=}\dfrac{3}{16}\times\dfrac{-7}{17}\text{=}\dfrac{-21}{272}\)

\(6.\dfrac{11}{23}\times\left(\dfrac{5}{9}+\dfrac{17}{9}-\dfrac{13}{9}\right)\text{=}\dfrac{11}{23}\times1\text{=}\dfrac{11}{23}\)

Mik làm từ trên xuống đưới nha

>

=

=

=

HT

dap an la 
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=
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\(\frac{\frac{3}{4}-\frac{3}{5}+\frac{3}{7}+\frac{3}{11}}{\frac{13}{4}-\frac{13}{5}+\frac{13}{7}+\frac{13}{11}}=\frac{3\left(\frac{1}{4}-\frac{1}{5}+\frac{1}{7}+\frac{1}{11}\right)}{13\left(\frac{1}{4}-\frac{1}{5}+\frac{1}{7}+\frac{1}{11}\right)}=\frac{3}{13}\)

\(\dfrac{-13}{4}.\dfrac{3}{7}-\dfrac{13}{4}.\dfrac{10}{7}-\dfrac{13}{7}\)

\(=\dfrac{13}{4}.\dfrac{-3}{7}-\dfrac{13}{4}.\dfrac{10}{7}-\dfrac{13}{7}\)

\(=\dfrac{13}{4}.\left(\dfrac{-3}{7}-\dfrac{10}{7}\right)-\dfrac{13}{7}\)

\(=\dfrac{13}{4}.\dfrac{-13}{7}-\dfrac{13}{7}\)

\(=\dfrac{-13}{4}.\dfrac{13}{7}-\dfrac{13}{7}\)

\(=\dfrac{13}{7}.\left(\dfrac{-13}{4}-1\right)\)

\(=\dfrac{13}{7}.-\dfrac{17}{4}\)

\(=-\dfrac{221}{28}\)

* Cách làm nhanh: Với biểu thức như trên, hai phân số nhân với nhau có thể đổi dấu cho nhau.*

-13/4 . 3/7 - 13/4 . 10/7 - 13/7

= -13/4 . (3/7 + 10/7) - 13/7

= -13/4 . 13/7 - 13/7

= 13/7 . (-13/4 - 1)

= 13/7 . (-17/4)

= -221/28