\(\frac{-5}{23}.\frac{17}{26}+\frac{-5}{23}.\frac{9}{26}=\frac{-5}{23}.\left(\frac{17}{26}+\frac{9}{26}\right)=\frac{-5}{23}.1=\frac{-5}{23}\)

\(\frac{-21}{20}+\frac{21}{20}.\frac{3}{4}+\frac{3}{4}=\frac{21}{20}.\left(\frac{3}{4}-1\right)+\frac{3}{4}=\frac{21}{20}.\frac{-1}{4}+\frac{3}{4}=\frac{1}{4}.\left(\frac{-21}{20}+\frac{3}{4}\right)=\frac{1}{4}.\left(-\frac{3}{10}\right)=-\frac{3}{40}\)

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

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

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

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

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

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

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

321 x 3 + 321 x 5 + 321 x 2

= 321 x (3 + 5 + 2)

= 321 x 10

= 3 210.

321 x 3 + 321 x 5 + 321 x 2

= 321 x (3 + 5 + 2)

= 321 x 10

= 3210

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

\(\frac{5}{23}x\left(\frac{17}{26}+\frac{9}{26}\right)\)=\(\frac{5}{23}x\frac{26}{26}\)=\(\frac{5}{23}x1\)=\(\frac{5}{23}\)

\(\frac{5}{23}\)x \(\frac{17}{26}+\frac{5}{23}\)x \(\frac{9}{26}\)

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

=\(\frac{5}{23}\)x \(\frac{26}{26}\)

=\(\frac{5}{23}\)x 1

=\(\frac{5}{23}\)

10

(90-26-14):5

=50 :5

=10

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

các bạn có ai biết giúp mình với . bạn nào trả lời đúng đầu tiên thì mình k luôn cho !

toán lớp mấy đấy,khó thật đấy ........

a,  3 . 5 2 - 16 : 2 2 = 3.25  - 16:4 = 75 - 4 = 71

b, 15.141 + 59.15 = 15.(141+59) = 15.200 = 3000

c,  2 3 . 17 - 2 3 . 14 = 8.17 - 8.14 = 8.(17 - 14) = 8.3 = 24

d, 20 - 30 - 5 - 1 2 = 20 - 30 - 4 2 = 20 - (30 - 16) = 20 - 14 = 6