Câu 2. Tính:
a) $\left ( \frac{3}{4} :1\frac{1}{2} \right ) - \left ( \frac{5}{6} : \frac{1}{3}\right )$
= $\left ( \frac{3}{4} :\frac{3}{2} \right ) - \left ( \frac{5}{6} . 3\right )$
= $\frac{1}{2} - \left ( \frac{5}{2} \right )$
= -2
b) $\left [ \left ( \frac{-1}{5}\right ) : \frac{1}{10}\right ] - \frac{5}{7} .\left ( \frac{2}{3} - \frac{1}{5} \right )$
= $-2 - \frac{5}{7} .\left ( \frac{2}{15} - \frac{1}{5} \right )$
= $-2 - \frac{5}{7} .\left ( \frac{10}{15} - \frac{3}{15} \right )$
= $-2 - \frac{5}{7} .\frac{7}{15} $
= $-2 - \frac{1}{3} $
= $- \frac{7}{3} $
c) $\left ( -0,4 \right ) + 2\frac{2}{5} . \left [ \left ( \frac{-2}{3} \right ) + \frac{1}{2} \right ]^{2}$
= $\left ( -0,4 \right ) +\frac{12}{5} . \left [ \left ( \frac{-4}{6} \right ) + \frac{3}{6} \right ]^{2}$
= $\left ( -0,4 \right ) +\frac{12}{5} . \left ( \frac{-1}{6} \right ) ^{2}$
= $\left ( -0,4 \right ) +\frac{12}{5} . \frac{1}{36}$
= $\left ( -\frac{2}{5}\right ) + \frac{1}{15}$
= $\left ( -\frac{6}{15}\right ) + \frac{1}{15}$
= $-\frac{6}{15}$
d) $\left \{ \left [ \left ( \frac{1}{25}-0,6 \right )^{2} : \frac{49}{125}\right ] .\frac{5}{6}\right \} - \left [ \left ( \frac{-1}{3} +\frac{1}{2} \right ) \right ]$
= $\left \{ \left [ \left ( \frac{1}{25}-\frac{3}{5} \right )^{2} : \frac{49}{125}\right ] .\frac{5}{6}\right \} - \left [ \left ( \frac{-2}{6} +\frac{3}{6} \right ) \right ]$
= $\left \{ \left [ \left (-\frac{14}{25} \right )^{2} : \frac{49}{125}\right ] .\frac{5}{6}\right \} - \frac{1}{6}$
= $\left \{ \left [ \frac{196}{245} : \frac{49}{125}\right ].\frac{5}{6}\right \} - \frac{1}{6}$
= $\left \{ \frac{4}{5}.\frac{5}{6}\right \} - \frac{1}{6}$
= $\frac{2}{3} - \frac{1}{6}$
= $\frac{1}{2}$