Giải câu 2 trang 14 toán VNEN 7 tập 1 .
a) ($\frac{-5}{11}$). $\frac{7}{15}$. ($\frac{11}{-5}$). (-30) = $\frac{7.(-30)}{15}$ = -14;
b) ($\frac{11}{12}$ : $\frac{33}{16}$). $\frac{3}{5}$ = ($\frac{11}{12}$ . $\frac{16}{33}$). $\frac{3}{5}$ = $\frac{11.16.3}{12.33.5}$ = $\frac{4.3}{3.3.5}$ = $\frac{4}{15}$;
c) (-$\frac{5}{9}$). $\frac{3}{11}$ + (-$\frac{13}{18}$). $\frac{3}{11}$ = $\frac{3}{11}$.[(-$\frac{5}{9}$) + (-$\frac{13}{18}$)] = $\frac{3}{11}$. $\frac{-23}{18}$ = $\frac{-23}{66}$.