Question

tính nhanh:

D=3/7(13/-8 -  7/9)-5/8(3/7 -  -8/15)

Answer 1

Ta có: \(D=\dfrac{3}{7}\left(\dfrac{13}{-8}-\dfrac{7}{9}\right)-\dfrac{5}{8}\left(\dfrac{3}{7}-\dfrac{-8}{15}\right)\)

\(=\dfrac{3}{7}\cdot\dfrac{-13}{8}-\dfrac{3}{7}\cdot\dfrac{7}{9}-\dfrac{5}{8}\cdot\dfrac{3}{7}-\dfrac{5}{8}\cdot\dfrac{8}{15}\)

\(=\dfrac{-39}{56}-\dfrac{3}{7}\left(\dfrac{7}{9}+\dfrac{5}{8}\right)-\dfrac{1}{3}\)

\(=\dfrac{-137}{84}\)

Answer 2

\(D=\dfrac{3}{7}(\dfrac{13}{-8}-\dfrac{7}{9})-\dfrac{5}{8}(\dfrac{3}{7}-\dfrac{-8}{15})\)

\(=(\dfrac{3}{7}. \dfrac{101}{105}).(\dfrac{-173}{72}-\dfrac{5}{8})\)

\(=\dfrac{101}{245}.\dfrac{-109}{36}\)

\(=\dfrac{593}{4410}\)