a)\(-\dfrac{2}{5}.\dfrac{4}{7}+\dfrac{-3}{5}.\dfrac{2}{7}+\dfrac{-3}{5}\)
=\(-\dfrac{2}{5}.\dfrac{4}{7}+\dfrac{3}{7}.\dfrac{-2}{5}+\dfrac{-3}{5}\)
=\(-\dfrac{2}{5}.\left(\dfrac{4}{7}+\dfrac{3}{7}\right)+\dfrac{-3}{5}\)
=\(\dfrac{-2}{5}.1+\dfrac{-3}{5}\)
=\(-\dfrac{2}{5}+\dfrac{-3}{5}\)
=\(-\dfrac{5}{5}\) = -1
\(\dfrac{5}{9}.\dfrac{14}{17}+\dfrac{1}{17}.\dfrac{5}{9}+\dfrac{2}{9}+\dfrac{5}{12}\)
=\(\dfrac{5}{9}.\left(\dfrac{14}{17}+\dfrac{1}{17}\right)+\dfrac{2}{9}+\dfrac{5}{12}\)
=\(\dfrac{5}{9}.\dfrac{15}{17}+\dfrac{2}{9}+\dfrac{5}{12}\)
=\(\dfrac{25}{51}+\dfrac{2}{9}+\dfrac{5}{12}\)
=\(\dfrac{691}{612}\)
\(-\dfrac{4}{25}:\dfrac{11}{79}+\dfrac{15}{11}:\dfrac{25}{79}\)
=\(-\dfrac{4}{25}.\dfrac{79}{11}+\dfrac{15}{11}.\dfrac{79}{25}\)
=\(-\dfrac{4}{25}.\dfrac{79}{11}+\dfrac{15}{25}.\dfrac{79}{11}\)
=\(\left(-\dfrac{4}{25}+\dfrac{15}{25}\right).\dfrac{79}{11}\)
=\(\dfrac{11}{25}.\dfrac{79}{11}\)
=\(\dfrac{79}{25}\)
