a; \(\dfrac{21}{11}\) x \(\dfrac{22}{17}\) x \(\dfrac{68}{63}\)

= \(\dfrac{21\times11\times2\times17\times4}{11\times17\times21\times3}\)

= \(\dfrac{11\times17\times21}{11\times17\times21}\) x \(\dfrac{2\times4}{3}\)

= 1 x \(\dfrac{8}{3}\)

= \(\dfrac{8}{3}\)

b; \(\dfrac{5}{14}\) \(\times\) \(\dfrac{7}{13}\) x \(\dfrac{26}{25}\)

= \(\dfrac{5\times7\times2\times13}{7\times2\times13\times5\times5}\)

= \(\dfrac{5\times7\times2\times13}{5\times7\times2\times13}\) x \(\dfrac{1}{5}\)

= 1 x \(\dfrac{1}{5}\)

= \(\dfrac{1}{5}\)

21/11 × 22/17 × 68/63

= (21 × 2 × 4)/63

= 8/3

21/11 x 22/17 x 68/63 = 952/357

5/14 x 7/13 x 6/25=3/65

\(\frac{21}{11}X\frac{22}{17}X\frac{68}{63}=\frac{952}{357} \)

\(\frac{5}{14}X\frac{7}{13}X\frac{6}{25}=\frac{3}{65}\)

ko iểu

21/11 x 22/17x68/63

= 7x3x2x11x4x17      /           11x17x7x3x3

=8/3

5/14x7/13x26/25

=5x7x26              /                14x13x25

= 5x7x13x2             /              7x2x13x5x5

=1/5

cậu có thể giảng kĩ hơn được ko mình ko hiểu 1 tí nào 

21 / 11 x 22 / 17 x 68 /63 

Sao khong ai giai bai nấy vậy nè.

a. mình ko biết

b. 5/14 x 7/13 x 26/26 = 5 x 7 x 13 x 2/7 x 2 x 13 x 5 = ( gạch các số giống nhau ở 2 vế ) + 1/5

a; \(\dfrac{21}{11}\) x \(\dfrac{22}{17}\) x \(\dfrac{68}{63}\)

= \(\dfrac{21\times11\times2\times17\times4}{11\times17\times21\times3}\)

= \(\dfrac{11\times17\times21}{11\times17\times21}\) x \(\dfrac{2\times4}{3}\)

= 1 x \(\dfrac{8}{3}\)

= \(\dfrac{8}{3}\)

b; \(\dfrac{5}{14}\) \(\times\) \(\dfrac{7}{13}\) x \(\dfrac{26}{25}\)

= \(\dfrac{5\times7\times2\times13}{7\times2\times13\times5\times5}\)

= \(\dfrac{5\times7\times2\times13}{5\times7\times2\times13}\) x \(\dfrac{1}{5}\)

= 1 x \(\dfrac{1}{5}\)

= \(\dfrac{1}{5}\)

Chúc bn học tốt!

8/3 vs 1/5

21/11*22/17*68/63

=22/11*68/17*21/63

=2*4*1/3

=8/3