Bài tập về thực hiện phép tính.
1.
M = $\frac{-3}{8}.1\frac{3}{5}+\frac{1}{7}\left ( -1\frac{1}{6} \right )$
= $\frac{-3}{8}.\frac{8}{5}+\frac{1}{7}.\frac{-7}{6}$
= $\frac{-3}{5}+\frac{-1}{6}$
= $\frac{-23}{30}$
N = $2\frac{1}{3}.\left ( -3\frac{1}{4} \right ).(-2,5)$
= $\frac{7}{3}.\frac{-13}{4}.\frac{-5}{2}$
= $\frac{455}{24}$
P = $\left ( \frac{3}{5}-0,2 \right ).\left ( 0,5-\frac{4}{5} \right )$
= $\left ( \frac{3}{5}-\frac{1}{5} \right ).\left ( \frac{1}{2}-\frac{4}{5} \right )$
= $\frac{2}{5}.\frac{-3}{10}$
= $\frac{-3}{25}$
Vậy M < P < N
2.
a) A = $\left ( \frac{2}{7}.\frac{1}{4}-\frac{1}{3}.\frac{2}{7} \right ):\left ( \frac{2}{7}.\frac{3}{9}-\frac{2}{7}.\frac{2}{5} \right )$
= $\left [\frac{2}{7}.\left ( \frac{1}{4}-\frac{1}{3} \right ) \right ]:\left [\frac{2}{7}.\left ( \frac{3}{9}-\frac{2}{5} \right ) \right ]$
= $\frac{-1}{12}:\frac{-1}{15}$
= $\frac{5}{4}$
b) B = $\frac{\left ( \frac{1}{5}-\frac{2}{7} \right ).\frac{3}{4}-\frac{3}{4}.\left ( \frac{1}{3}-\frac{2}{7} \right )}{\frac{1}{5}.\frac{2}{7}-\frac{1}{3}.\left ( \frac{2}{7}+\frac{3}{9} \right )+\frac{3}{9}.\frac{1}{5}}$
= $\frac{\frac{3}{4}.\left ( \frac{1}{5}-\frac{2}{7}-\frac{1}{3}+\frac{2}{7} \right )}{\frac{1}{5}.\left (\frac{2}{7}+\frac{1}{3} \right )-\frac{1}{3}.\left ( \frac{2}{7}+\frac{1}{3} \right )}$
= $\frac{\frac{3}{4}.\left ( \frac{1}{5}-\frac{1}{3} \right )}{\left ( \frac{1}{5}-\frac{1}{3} \right ).\left ( \frac{2}{7}+\frac{1}{3} \right )}$
= $\frac{63}{52}$
3. M = $\frac{1}{2}.\frac{1}{-3}+\frac{1}{-3}.\frac{1}{4}+\frac{1}{4}.\frac{1}{-5}+\frac{1}{-5}.\frac{1}{6}$
= $-\left ( \frac{1}{2}.\frac{1}{3}+\frac{1}{3}.\frac{1}{4}+\frac{1}{4}.\frac{1}{5}+\frac{1}{5}.\frac{1}{6} \right )$
= $-\left ( \frac{1}{2}-\frac{1}{3}+\frac{1}{3}-\frac{1}{4}+\frac{1}{4}-\frac{1}{5}+\frac{1}{5}-\frac{1}{6} \right )$
= $-\left ( \frac{1}{2}-\frac{1}{6} \right )$
= $\frac{-1}{3}$