Question

3/ Tính hợp lí :

a/ P = \(\dfrac{-2}{7}\) + \(\dfrac{14}{29}\) + \(\dfrac{12}{33}\) + \(\dfrac{15}{29}\) + \(\dfrac{21}{33}\) + \(\dfrac{2}{7}\)

b/ \(\dfrac{2}{7}\) . \(\dfrac{5}{19}\) + \(\dfrac{2}{7}\) . \(\dfrac{14}{19}\) + \(\dfrac{21}{19}\) - \(\dfrac{2}{7}\) . \(\dfrac{1}{5}\)

Answer 1

a)P=\(\dfrac{-2}{7}+\dfrac{14}{29}+\dfrac{12}{33}+\dfrac{15}{29}+\dfrac{21}{33}+\dfrac{2}{7}\)

      =\(\left(\dfrac{-2}{7}+\dfrac{2}{7}\right)+\left(\dfrac{14}{29}+\dfrac{15}{29}\right)+\left(\dfrac{12}{33}+\dfrac{21}{33}\right)\)

      =0+1+1=2

b)\(\dfrac{2}{7}.\dfrac{5}{19}+\dfrac{2}{7}.\dfrac{14}{19}+\dfrac{21}{19}-\dfrac{2}{7}.\dfrac{1}{5}\)

=\(\dfrac{2}{7}.\left(\dfrac{5}{19}+\dfrac{14}{19}-\dfrac{1}{5}\right)+\dfrac{21}{19}\)

=\(\dfrac{2}{7}.\dfrac{4}{5}+\dfrac{21}{19}=\dfrac{887}{665}\)