Đáp án:
$a)\dfrac{2453}{82}\\
b)
\dfrac{1032}{35}\\
c)
\dfrac{-5}{11}\\
d)
\dfrac{503}{1938}\\
e)
1\\
g)
\dfrac{306}{35}\\$
Giải thích các bước giải:
$a)49\dfrac{8}{23}-\left ( 5\dfrac{7}{82}+14\dfrac{8}{23} \right )\\
=49\dfrac{8}{23}-5\dfrac{7}{82}-14\dfrac{8}{23} \\
=(49-14)+\left ( \dfrac{8}{23}-\dfrac{8}{23} \right )-\dfrac{417}{82}\\
=35-\dfrac{417}{82}\\
=\dfrac{35.82}{82}-\dfrac{417}{82}\\
=\dfrac{2453}{82}\\
b)
71\dfrac{38}{45}-\left ( 43\dfrac{38}{45}-1\dfrac{17}{5.7} \right )\\
=71\dfrac{38}{45}- 43\dfrac{38}{45}+1\dfrac{17}{35}\\
=(71-43)+\left (\dfrac{38}{45}-\dfrac{38}{45} \right )+\dfrac{52}{35}\\
=28+\dfrac{52}{35}\\
=\dfrac{28.35}{35}+\dfrac{52}{35}\\
=\dfrac{1032}{35}\\
c)
\dfrac{5}{7}.\dfrac{5}{11}+\dfrac{5}{7}.\dfrac{2}{11}-\dfrac{5}{7}.\dfrac{14}{11}\\
=\dfrac{5}{7}.\left ( \dfrac{5}{11}+\dfrac{2}{11}-\dfrac{14}{11} \right )\\
=\dfrac{5}{7}.\dfrac{-7}{11}\\
=\dfrac{-5}{11}\\
d)
\dfrac{-2}{17}+\dfrac{15}{23}+\dfrac{-15}{18}+\dfrac{4}{19}+\dfrac{8}{23}\\
=\dfrac{-2}{17}+\left (\dfrac{15}{23} +\dfrac{8}{23} \right )+\dfrac{-15}{18}+\dfrac{4}{19}\\
=\dfrac{-2}{17}+1+\dfrac{-15}{18}+\dfrac{4}{19}\\
=\dfrac{(-2).18.19}{17.18.19}+\dfrac{17.18.19}{17.18.19}+\dfrac{(-15).17.19}{17.18.19}+\dfrac{4.17.18}{17.18.19}\\
=\dfrac{1509}{5814}\\
=\dfrac{503}{1938}\\
e)
1\dfrac{5}{13}+\dfrac{-3}{8}+\dfrac{8}{13}+\dfrac{-5}{8}\\
=\dfrac{18}{13}+\dfrac{8}{13}+\dfrac{-3}{8}+\dfrac{-5}{8}\\
=\dfrac{26}{13}+\dfrac{-8}{8}\\
=2-1=1\\
g)
\left ( 19\dfrac{5}{8}:\dfrac{7}{12}-13\dfrac{1}{4}:\dfrac{7}{12} \right ).\dfrac{4}{5}\\
=\left ( \dfrac{157}{8}-\dfrac{53}{4}\right ).\dfrac{12}{7} .\dfrac{4}{5}\\
=\left ( \dfrac{157}{8}-\dfrac{53.2}{8}\right ).\dfrac{12}{7} .\dfrac{4}{5}\\
=\dfrac{51}{8}.\dfrac{48}{35}\\
=\dfrac{306}{35}\\$
