Найдите значение выражения (7/20 - 8/15)в квадрате + 4/5 *(7/20 - 9/16)

Решите задачу:

$(\frac{7}{20}- \frac{8}{15})^2+ \frac{4}{5}*( \frac{7}{20}- \frac{9}{16} )= \frac{2413}{3600} \\ \\ 1) \frac{7}{20}- \frac{9}{16}= \frac{28-45}{80}=- \frac{17}{80} \\ \\2) - \frac{17}{80}* \frac{4}{5}=- \frac{17}{100} \\ \\ 3) ( \frac{7}{20}- \frac{8}{15})^2= (\frac{7}{20})^2-2* \frac{7}{20}* \frac{8}{15}+( \frac{8}{15})^2= \frac{49}{400}- \frac{112}{300}+ \frac{64}{225}= \\ \\ \frac{49}{16}- \frac{112}{12}+ \frac{64}{9}= \frac{147-448}{48}+ \frac{64}{9}=$ $- \frac{301}{48}+ \frac{64}{9} = \frac{-2709+3072}{432}= \frac{363}{432} \\ \\ 4) \frac{-17}{100}+ \frac{363}{432}= \frac{-7344+36300}{43200}= \frac{28956}{43200}= \frac{2413}{3600}$