a, -3/4 + 3/7 + -1/4 + 4/9 + 4/7
=(−34+−14)+(37+47)+49(−34+−14)+(37+47)+49
=−1+1+49−1+1+49
=49
b. \(\dfrac{-7}{9}.\dfrac{4}{11}+\dfrac{-7}{9}.\dfrac{7}{11}+\dfrac{52}{9}\)
= \(\dfrac{-7}{9}.\left(\dfrac{4}{11}+\dfrac{7}{11}\right)+\dfrac{52}{9}\)
= \(\dfrac{-7}{9}.1+\dfrac{52}{9}\)
= \(\dfrac{-7}{9}+\dfrac{52}{9}\)
= \(\dfrac{45}{9}\)
Chúc bạn học tốt!! ^^
\(a\)) \(\dfrac{-3}{4}+\dfrac{3}{7}+\dfrac{-1}{4}+\dfrac{4}{9}+\dfrac{4}{7}\)
\(=\left(\dfrac{-3}{4}+\dfrac{-1}{4}\right)+\left(\dfrac{3}{7}+\dfrac{4}{7}\right)+\dfrac{4}{9}\)
\(=-1+1+\dfrac{4}{9}\)
\(=0+\dfrac{4}{9}=\dfrac{4}{9}\)
\(b\)) \(\dfrac{-7}{9}.\dfrac{4}{11}+\dfrac{-7}{9}.\dfrac{7}{11}+\dfrac{52}{9}\)
\(=\dfrac{-7}{9}.\left(\dfrac{4}{11}+\dfrac{7}{11}\right)+\dfrac{52}{9}\)
\(=\dfrac{-7}{9}.1+\dfrac{52}{9}\)
\(=\dfrac{-7}{9}+\dfrac{52}{9}=5\)
\(c\)) \(\left(\dfrac{21}{31}+\dfrac{2013}{6039}\right)-\left(\dfrac{44}{53}-\dfrac{10}{31}\right)-\dfrac{9}{53}\)
\(=\left(\dfrac{21}{31}+\dfrac{1}{3}\right)-\left(\dfrac{44}{53}-\dfrac{10}{31}\right)-\dfrac{9}{53}\)
\(=\)_______________________\(\left(\text{sory tớ ko làm đc nữa}\right)\)
\(\text{bạn ơi làm đc òi: }\)
\(c\)) \(\left(\dfrac{21}{31}+\dfrac{2013}{6039}\right)-\left(\dfrac{44}{53}-\dfrac{10}{31}\right)-\dfrac{9}{53}\)
\(=\left(\dfrac{21}{31}+\dfrac{11}{31}\right)-\left(\dfrac{44}{53}+\dfrac{9}{53}\right)+\dfrac{1}{3}\)
\(=1-1+\dfrac{1}{3}=0+\dfrac{1}{3}=\dfrac{1}{3}\)
