\(\frac{321}{679}\)

a = 3/54 + 5/126 + 7/294 + 8/609 + 13/1218

=> a = 3/6.9 + 5/9.14 + 7/14.21 + 8/21.29 + 13/29.42

=> a = 1/6 - 1/9 + 1/9 - 1/14 + 1/14 - 1/21 + 1/21 - 1/29 + 1/29 - 1/42

=> a = 1/6 - 1/42

=> a = 7/42 - 1/42

=> a = 6/42 = 1/7

\(\frac{-3}{5}.\left(\frac{5}{7}+\frac{3}{7}+\frac{6}{7}\right)\)

=\(\frac{-3}{5}.\)\(\frac{14}{7}\)

=\(-\frac{3}{5}.2\)

=-6/5

\(\frac{3}{54}+\frac{5}{126}+\frac{7}{294}+\frac{8}{609}\) 

\(=\frac{3}{6.9}+\frac{5}{9.14}+\frac{7}{14.21}+\frac{8}{21.29}\) 

\(=\frac{1}{6}-\frac{1}{9}+\frac{1}{9}-\frac{1}{14}+\frac{1}{14}-\frac{1}{21}+\frac{1}{21}-\frac{1}{29}\)

\(=\frac{1}{6}-\frac{1}{29}=\frac{23}{174}\)

lm ơn giúp mk nha

làm xong mk tk cho

\(=-\frac{5}{7}\cdot\left(\frac{2}{11}+\frac{9}{14}\right)+\frac{12}{7}\)

\(=-\frac{5}{7}\cdot\frac{127}{154}+\frac{12}{7}\)

\(=-\frac{635}{1078}+\frac{12}{7}=\frac{1213}{1078}\)

kt lại đề bài xem hình như sai ở đâu mà số to thế

=-5/7.(2/11+9/14)+1 5/7

=-5/7.127/154+12/7

=635/1078+12/7

=2483/1078

MK ko chắc nữa nha

\(\frac{5}{24}+\frac{5}{104}+\frac{5}{234}+\frac{5}{414}\)

\(=\frac{5}{3.8}+\frac{5}{8.13}+\frac{5}{13.18}+\frac{5}{18.23}\)

\(=\frac{1}{3}-\frac{1}{8}+\frac{1}{8}-\frac{1}{13}+\frac{1}{13}-\frac{1}{18}+\frac{1}{18}-\frac{1}{23}\)

\(=\frac{1}{3}-\frac{1}{23}=\frac{20}{69}\)

\(\frac{5}{24}+\frac{5}{104}+\frac{5}{234}+\frac{5}{414}\)

\(=\frac{5}{3.8}+\frac{5}{8.13}+\frac{5}{13.18}+\frac{5}{18.23}\)

\(=\frac{1}{3}-\frac{1}{8}+\frac{1}{8}-\frac{1}{13}+\frac{1}{13}-\frac{1}{18}+\frac{1}{18}-\frac{1}{23}\)

\(=\frac{1}{3}-\frac{1}{23}\)

\(=\frac{20}{69}\)