5/23 : ( 3/26 + 7/9) - 5/23 : (23/26 + 2/9)

=\(\frac{5}{23}\)\(\div[(\frac{3}{26}+\frac{7}{9})-(\frac{23}{26}+\frac{2}{9})]\)

=\(\frac{5}{23}\div\)\([(\frac{3}{26}+\frac{23}{26})-(\frac{7}{9}+\frac{2}{9})]\)

=\(\frac{5}{23}\div[1-1]\) 

=\(\frac{5}{23}\div0\) 

=0

5/23 : ( 3/26 + 7/9 ) - 5/23 : ( 23/26 + 2/9 )

=5/23 : { (23/26 + 3/26) - ( 7/9 + 2/9 )

=5/23 : { 1-1 }

=5/23 : 0

=0

a) Ta có: \(\dfrac{21}{25}\cdot\dfrac{11}{9}\cdot\dfrac{5}{7}\)

\(=\dfrac{21\cdot11\cdot5}{25\cdot9\cdot7}\)

\(=\dfrac{3\cdot7\cdot11\cdot5}{5\cdot5\cdot3\cdot3\cdot7}\)

\(=\dfrac{11}{5\cdot3}=\dfrac{11}{15}\)

a) 21/25. 11/9. 5/7

=(21/25.5/7).11/9

= 3/5. 11/9

=11/15

b) 5/23 . 17/26 . 5/23 . 9/26

=5/23.( 17/26+9/26)

=5/23. 1

=5/23

b) Ta có: \(\dfrac{5}{23}\cdot\dfrac{17}{26}+\dfrac{5}{23}\cdot\dfrac{9}{26}\)

\(=\dfrac{5}{23}\left(\dfrac{17}{26}+\dfrac{9}{26}\right)\)

\(=\dfrac{5}{23}\cdot1=\dfrac{5}{23}\)

\(\dfrac{-5}{23}\cdot\dfrac{17}{26}+\dfrac{5}{23}\cdot\dfrac{9}{-29}\)

= \(\dfrac{5}{23}\cdot\dfrac{-17}{26}+\dfrac{5}{23}\cdot\dfrac{-9}{29}\)

= \(\dfrac{5}{23}\left(\dfrac{-17}{26}+\dfrac{-9}{26}\right)\)

= \(\dfrac{5}{23}\cdot\left(-1\right)=\dfrac{-5}{23}\)

\(\dfrac{-5}{23}.\dfrac{17}{26}+\dfrac{5}{23}.\dfrac{9}{-26}=\dfrac{-5}{23}.\left(\dfrac{17}{26}+\dfrac{9}{26}\right)\)

\(=\dfrac{-5}{23}.\left(\dfrac{17+9}{26}\right)=\dfrac{-5}{23}.\dfrac{26}{26}\)

\(=\dfrac{-5}{23}.1=\dfrac{-5}{23}\)

a. bằng77

b. bằng 13

lớp 2 đã học cái này rồi à

a. bằng77

b. bằng 13

câu nầy hơn khó nên mình ko giải đc bạn đợ mình giải đã

1) 2763 + 152 = 2951

2)(-7) + (-14) = -21

3)(-35) + (-9) =-44

4) (-5) + (-248) = -253 

\(\dfrac{-5}{23}\cdot\dfrac{17}{26}+\dfrac{5}{-23}\cdot\dfrac{9}{26}\)

= \(\dfrac{-5}{23}\cdot\dfrac{17}{26}+\dfrac{-5}{23}\cdot\dfrac{9}{26}\)

= \(\dfrac{-5}{23}\left(\dfrac{17}{26}+\dfrac{9}{26}\right)\)

= \(\dfrac{-5}{23}\cdot1=\dfrac{-5}{23}\)

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