Đáp án:
$a)
\dfrac{-284}{105}\\
b)
\dfrac{-23}{12}\\
c)
\dfrac{-91}{60}\\
d) \dfrac{179}{56}$
Giải thích các bước giải:
$a)
\dfrac{3}{7}+\left ( -\dfrac{9}{5} \right )-\dfrac{4}{3}\\
=\dfrac{3}{7} -\dfrac{9}{5} -\dfrac{4}{3}\\
=\dfrac{3.15}{105} -\dfrac{9.21}{105} -\dfrac{4.35}{105}\\
=\dfrac{-284}{105}\\
b)
-0,5+\left ( -\dfrac{3}{4} \right )+\left ( -\dfrac{2}{3} \right )\\
=\dfrac{-1}{2}-\dfrac{3}{4}-\dfrac{2}{3}\\
=\dfrac{-6}{12}-\dfrac{9}{12}-\dfrac{8}{12}\\
=\dfrac{-23}{12}\\
c)
\dfrac{1}{3}-\left ( -1\dfrac{2}{5} \right )+\left ( -3\dfrac{1}{4} \right )\\
=\dfrac{1}{3}+\dfrac{7}{5}-\dfrac{13}{4}\\
=\dfrac{20}{60}+\dfrac{7.12}{60}-\dfrac{13.15}{60}\\
=\dfrac{-91}{60}\\
d) \dfrac{3}{2}-\left [ \left ( -\dfrac{4}{7} \right ) -\left ( \dfrac{1}{2}+\dfrac{5}{8} \right )\right ]\\
=\dfrac{3}{2}+\dfrac{4}{7}+\dfrac{1}{2}+\dfrac{5}{8}\\
=\dfrac{3}{2}+\dfrac{1}{2}+\dfrac{4}{7}+\dfrac{5}{8}\\
=2-\dfrac{4}{7}+\dfrac{5}{8}\\
=\dfrac{2.56}{56}+\dfrac{4.8}{56}+\dfrac{5.7}{56}\\
=\dfrac{179}{56}$
