e) \(\dfrac{-3}{7}\) . \(\dfrac{8}{19}\) + \(\dfrac{3}{7}\) . \(\dfrac{-11}{19}\) -  \(3\dfrac{1}{3}\)

= \(\dfrac{-3}{7}\) . \(\dfrac{8}{19}\) - \(\dfrac{-3}{7}\) . \(\dfrac{-11}{19}\) - \(\dfrac{10}{3}\)

= \(\dfrac{-3}{7}\) . ( \(\dfrac{8}{19}\) - \(\dfrac{-11}{19}\) ) - \(\dfrac{10}{3}\)

= \(\dfrac{-3}{7}\) . ( \(\dfrac{8}{19}\) + \(\dfrac{11}{19}\) ) - \(\dfrac{10}{3}\)

= \(\dfrac{-3}{7}\) . 1 - \(\dfrac{10}{3}\)

= \(\dfrac{-3}{7}\) - \(\dfrac{10}{3}\)

= \(\dfrac{-9}{21}\) - \(\dfrac{70}{21}\)

= \(\dfrac{-9}{21}\) + \(\dfrac{-70}{21}\)

= \(\dfrac{-79}{21}\)

d) \(\dfrac{6}{11}\) . \(\dfrac{-4}{5}\) + \(\dfrac{4}{5}\) . \(\dfrac{-5}{11}\) + \(1\dfrac{1}{2}\)

= \(\dfrac{6}{11}\) . \(\dfrac{-4}{5}\) - \(\dfrac{-4}{5}\) . \(\dfrac{-5}{11}\) + \(\dfrac{3}{2}\)

= \(\dfrac{-4}{5}\) . ( \(\dfrac{6}{11}\) - \(\dfrac{-5}{11}\) ) + \(\dfrac{3}{2}\)

= \(\dfrac{-4}{5}\) . ( \(\dfrac{6}{11}\) + \(\dfrac{5}{11}\) ) + \(\dfrac{3}{2}\)

= \(\dfrac{-4}{5}\) . 1 + \(\dfrac{3}{2}\)

= \(\dfrac{-4}{5}\) + \(\dfrac{3}{2}\)

= \(\dfrac{-8}{10}\) + \(\dfrac{15}{10}\)

= \(\dfrac{7}{10}\)

c) \(\dfrac{4}{21}\) . \(\dfrac{-5}{7}\) + \(\dfrac{-5}{7}\) . \(\dfrac{15}{21}\) + \(\dfrac{-5}{7}\) . \(\dfrac{2}{21}\)

= \(\dfrac{-5}{7}\) . ( \(\dfrac{4}{21}\) + \(\dfrac{15}{21}\) + \(\dfrac{2}{21}\) )

= \(\dfrac{-5}{7}\) . 1

= \(\dfrac{-5}{7}\)

b) \(\dfrac{-6}{7}\) . \(\dfrac{3}{5}\) +\(\dfrac{-6}{7}\) .\(\dfrac{2}{5}\) - \(1\dfrac{1}{3}\)

= \(\dfrac{-6}{7}\) . \(\dfrac{3}{5}\) +\(\dfrac{-6}{7}\) .\(\dfrac{2}{5}\) - \(\dfrac{4}{3}\) 

= \(\dfrac{-6}{7}\) . (\(\dfrac{3}{5}\) + \(\dfrac{2}{5}\) ) - \(\dfrac{4}{3}\) 

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

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

= \(\dfrac{-18}{21}\) - \(\dfrac{28}{21}\)

= \(\dfrac{-18}{21}\) + \(\dfrac{-28}{21}\)

= \(\dfrac{-46}{21}\)

a) \(\dfrac{-7}{5}\) . \(\dfrac{4}{23}\)  + \(\dfrac{4}{23}\) . \(\dfrac{2}{5}\)

= \(\dfrac{4}{23}\) . ( \(\dfrac{-7}{5}\) + \(\dfrac{2}{5}\) )

= \(\dfrac{4}{23}\) . -1

= \(\dfrac{-4}{23}\)

a. Thời gian âm thanh truyền từ xe tăng đến pháo thủ:

                              t = 2,1-0,6 = 1,5 (s)

Khoảng cách từ khẩu pháo đến xe tăng :

                         s = v . t = 340 .1,5 = 495 (m)

b. Tốc độ của đạn:

V = \(\dfrac{s}{T}\) = \(\dfrac{495}{0,6}\) = 825 (m/s)

Nhiệt độ đêm hôm đó ở Moscow là:

-7 - 3 = 10*C