Question

[Trâm Nguyễn]

Thực hiện phép tính (tính hợp lí nếu có thể)

a) \(\dfrac{-3}{5}\) + \(\dfrac{28}{5}\) . ( \(\dfrac{13}{56}\) - \(\dfrac{5}{24}\) + \(\dfrac{1}{7}\) )

b) \(\dfrac{5}{7}\) . \(\dfrac{11}{18}\) + \(\dfrac{3}{7}\) . \(\dfrac{5}{8}\) + \(\dfrac{4}{9}\)

c) 4\(\dfrac{5}{9}\) : ( \(\dfrac{-5}{7}\) ) + \(\dfrac{49}{9}\) : ( \(\dfrac{-5}{7}\) )

GIÚP EM VỚI Ạ

Answer 1

[Dang Tung]

a) \(\dfrac{-3}{5}+\dfrac{28}{5}.\left(\dfrac{13}{56}-\dfrac{5}{24}+\dfrac{1}{7}\right)\\ =-\dfrac{3}{5}+\dfrac{28}{5}.\dfrac{13}{56}-\dfrac{28}{5}.\dfrac{5}{24}+\dfrac{28}{5}.\dfrac{1}{7}\\ =-\dfrac{3}{5}+\dfrac{28.13}{5.2.28}-\dfrac{4.7.5}{5.4.6}+\dfrac{4.7.1}{5.7}\\ =-\dfrac{3}{5}+\dfrac{13}{10}-\dfrac{7}{6}+\dfrac{4}{5}\\ =\dfrac{1}{5}+\dfrac{13}{10}-\dfrac{7}{6}\\ =\dfrac{6}{30}+\dfrac{39}{30}-\dfrac{35}{30}=\dfrac{10}{30}=\dfrac{1}{3}\)

b) \(\dfrac{5}{7}.\dfrac{11}{18}+\dfrac{3}{7}.\dfrac{5}{8}+\dfrac{4}{9}\\ =\dfrac{5}{7}.\dfrac{11}{18}+\dfrac{5}{7}.\dfrac{3}{8}+\dfrac{4}{9}\\ =\dfrac{5}{7}.\left(\dfrac{11}{18}+\dfrac{3}{8}\right)+\dfrac{4}{9}\\ =\dfrac{5}{7}.\dfrac{7}{4}+\dfrac{4}{9}\\ =\dfrac{5}{4}+\dfrac{4}{9}=\dfrac{61}{36}\)

c) \(4\dfrac{5}{9}:\left(\dfrac{-5}{7}\right)+\dfrac{49}{9}:\left(\dfrac{-5}{7}\right)\\=\left(4\dfrac{5}{9}+\dfrac{49}{9}\right):\dfrac{-5}{7}\\ =\left(\dfrac{41}{9}+\dfrac{49}{9}\right).\dfrac{-7}{5}\\ =10.\dfrac{-7}{5}=-14\)

Answer 2

[Dang Tung]

Mình sửa lại câu b nhé:

\(=\dfrac{5}{7}.\dfrac{11}{18}+\dfrac{5}{7}.\dfrac{3}{8}+\dfrac{4}{9}\\ =\dfrac{5}{7}.\left(\dfrac{11}{18}+\dfrac{3}{8}\right)+\dfrac{4}{9}\\ =\dfrac{5}{7}.\dfrac{71}{72}+\dfrac{4}{9}=\dfrac{355}{504}+\dfrac{4}{9}\\ =\dfrac{193}{168}\)