Question

[Pham Thi Thao Trang]

giup minh bai 2 voi a

Answer 1

[Nguyễn Lê Phước Thịnh]

1: \(\dfrac{1}{4}+\dfrac{3}{4}:\dfrac{-6}{7}\)

\(=\dfrac{1}{4}-\dfrac{3}{4}\cdot\dfrac{7}{6}\)

\(=\dfrac{1}{4}-\dfrac{7}{8}=\dfrac{2}{8}-\dfrac{7}{8}=-\dfrac{5}{8}\)

2: \(\left(\dfrac{3}{8}+\dfrac{-3}{4}+\dfrac{7}{12}\right):\dfrac{5}{6}+\dfrac{1}{2}\)

\(=\left(\dfrac{9}{24}-\dfrac{18}{24}+\dfrac{14}{24}\right)\cdot\dfrac{6}{5}+\dfrac{1}{2}\)

\(=\dfrac{5}{24}\cdot\dfrac{6}{5}+\dfrac{1}{2}=\dfrac{1}{4}+\dfrac{1}{2}=\dfrac{3}{4}\)

3: \(\left(\dfrac{7}{8}-\dfrac{3}{4}\right)\cdot1\dfrac{1}{3}-\dfrac{2}{7}\left(3,5\right)^2\)

\(=\dfrac{1}{8}\cdot\dfrac{4}{3}-\dfrac{2}{7}\cdot\dfrac{49}{4}\)

\(=\dfrac{1}{6}-\dfrac{7}{2}=\dfrac{1}{6}-\dfrac{21}{6}=-\dfrac{20}{6}=-\dfrac{10}{3}\)

4: \(\dfrac{31}{45}-\left(\dfrac{8}{59}-\dfrac{14}{45}\right)=\dfrac{31}{45}-\dfrac{8}{59}+\dfrac{14}{45}\)

\(=1-\dfrac{8}{59}=\dfrac{51}{59}\)

5: \(\dfrac{\dfrac{2}{3}+\dfrac{2}{7}-\dfrac{2}{14}}{\dfrac{3}{3}+\dfrac{3}{7}-\dfrac{3}{14}}=\dfrac{2\left(\dfrac{1}{3}+\dfrac{1}{7}-\dfrac{1}{14}\right)}{3\left(\dfrac{1}{3}+\dfrac{1}{7}-\dfrac{1}{14}\right)}=\dfrac{2}{3}\)

8: \(\dfrac{-3}{17}\cdot\dfrac{5}{9}+\dfrac{4}{9}\cdot\dfrac{-3}{17}+137\dfrac{3}{17}\)

\(=\dfrac{3}{17}\left(-\dfrac{5}{9}-\dfrac{4}{9}\right)+137+\dfrac{3}{17}\)

\(=-\dfrac{3}{17}+137+\dfrac{3}{17}=137\)

9: \(\left(19\dfrac{5}{8}:\dfrac{7}{12}-13\dfrac{1}{4}:\dfrac{7}{12}\right)\cdot\dfrac{4}{5}\)

\(=\left(\dfrac{12}{7}\cdot\dfrac{157}{8}-\dfrac{12}{7}\cdot\dfrac{53}{4}\right)\cdot\dfrac{4}{5}\)

\(=\dfrac{12}{7}\left(\dfrac{157}{8}-\dfrac{53}{4}\right)\cdot\dfrac{4}{5}\)

\(=\dfrac{12}{7}\cdot\dfrac{51}{8}\cdot\dfrac{4}{5}=\dfrac{306}{35}\)