a. \(\frac{4}{5}+\frac{3}{7}=\frac{28}{35}+\frac{15}{35}=\frac{43}{35}\)     ;   \(\frac{6}{8}+\frac{4}{2}=\frac{6}{8}+\frac{16}{8}=\frac{22}{8}=\frac{11}{4}\)

   \(\frac{9}{7}-\frac{7}{9}=\frac{81}{63}-\frac{49}{63}=\frac{32}{63}\);  \(\frac{8}{7}-\frac{7}{8}=\frac{64}{56}-\frac{49}{56}=\frac{15}{56}\)

b. \(\frac{7}{5}+\frac{6}{8}\div\frac{2}{5}=\frac{7}{5}+\frac{15}{8}=\frac{131}{40}\); \(\frac{3}{2}-\frac{2}{3}+\frac{4}{6}=\frac{5}{6}+\frac{4}{6}=\frac{9}{6}=\frac{3}{2}\)

\(\frac{6}{7}\times\frac{3}{4}-\frac{4}{3}=\frac{18}{28}-\frac{4}{3}=-\frac{29}{42}\)

a) \(\frac{4}{5}+\frac{3}{7}=\frac{43}{35}\); \(\frac{6}{8}+\frac{4}{2}=\frac{11}{4}\)

\(\frac{9}{7}-\frac{7}{9}=\frac{32}{63}\) ; \(\frac{8}{7}-\frac{7}{8}=\frac{15}{56}\)

b) \(\frac{7}{5}+\frac{6}{8}:\frac{2}{5}=\frac{7}{5}+\frac{15}{8}=\frac{131}{40}\)

\(\frac{3}{2}-\frac{2}{3}+\frac{4}{6}=\frac{3}{2}\);\(\frac{6}{7}\times\frac{3}{4}-\frac{4}{3}=-\frac{23}{42}\)

a. 4/5 + 3/7 = 28/35 + 15/35 = 43/35

    6/8 + 4/2 = 6/8 + 16/8 = 22/8 = 11/4

    9/7 - 7/9 = 81/63 - 49/63 = 32/63

    8/7 - 7/8 = 64/56 - 49/56 = 15/56

b. 7/5 + 6/8 : 2/5 = 7/5 + 15/8 = 56/40 + 75/40 = 131/40

   3/2 - 2/3 + 4/6 = 9/6 - 4/6 + 4/6 = 9/6 = 3/2

   6/7 x 3/4 - 4/3 = 9/14 - 4/3 = 27/42 - 56/42 = -29/42 

1.Tính

a . 4/5 + 3/7 = 28/35 + 15/35 = 43/35 

b. 6/8 + 4/2 = 2/3 + 2 = 8/3 

c. 9/7 - 7/9 = 81/63 - 49/63 = 32/63 

d. 7/5 + 6/8 : 2/5 

= 7/5 + 6/8 x 5/2 

= 7/5 + 15/8

= 56/40 + 75/40 = 131/40 

e. 3/2 - 2/3 + 4/6 

= 9/6 - 4/6 + 4/6

= 5/6 + 4/6

= 9/6 = 3/2

f. 6/7x  3/4 - 4/ 3

= 9/14 - 4/3 

= 27/42 - 56/42 

= 29/42 

tk ủng hộ mk nha 

mà bn ơi bài f. á mk thấy sao ấy lớp 4 chưa hok đến số nguyn âm đâu!hjhj theo mk thôi nha....