Đáp án:
$a)\dfrac{-41}{2}\\
b)
\dfrac{14}{11}\\
c)6$
Giải thích các bước giải:
$a)5\dfrac{1}{2}-14\dfrac{3}{7}:\dfrac{9}{13}-3\dfrac{4}{7}:\dfrac{9}{13}\\
=\dfrac{11}{2}-14\dfrac{3}{7}.\dfrac{13}{9}-3\dfrac{4}{7}.\dfrac{13}{9}\\
=\dfrac{11}{2}-\dfrac{13}{9}\left (14\dfrac{3}{7}+3\dfrac{4}{7} \right )\\
=\dfrac{11}{2}-\dfrac{13}{9}.18\\
=\dfrac{11}{2}-13.2\\
=\dfrac{11}{2}-\dfrac{26.2}{2}\\
=\dfrac{-41}{2}\\
b)
\dfrac{38}{45}-\left ( \dfrac{8}{45}-\dfrac{17}{51}-\dfrac{3}{11} \right )\\
=\dfrac{38}{45}-\dfrac{8}{45}+\dfrac{17}{51}+\dfrac{3}{11}\\
=\dfrac{30}{45}+\dfrac{17:17}{51:17}+\dfrac{3}{11}\\
=\dfrac{2}{3}+\dfrac{1}{3}+\dfrac{3}{11}\\
=\dfrac{2+1}{3}+\dfrac{3}{11}\\
=1+\dfrac{3}{11}\\
=\dfrac{11}{11}+\dfrac{3}{11}\\
=\dfrac{14}{11}\\
c)2\dfrac{1}{2}+19\dfrac{3}{11}.\dfrac{7}{26}-6\dfrac{3}{11}.\dfrac{7}{26}\\
=2\dfrac{1}{2}+\dfrac{7}{26}\left (19\dfrac{3}{11}-6\dfrac{3}{11} \right )\\
=\dfrac{5}{2}+\dfrac{7}{26}.13\\
=\dfrac{5}{2}+\dfrac{7}{2}\\
=\dfrac{12}{2}\\
=6$
