Giải thích các bước giải: image

Đáp án:

 $1)
0\\
2) \dfrac{77}{30}\\
3) \dfrac{11}{20}\\
4)
5\\
5)
\dfrac{50}{7}\\
6) -8\\
7) 12\\
8)
\dfrac{11}{20}\\
9) \dfrac{109}{27}\\
10) \dfrac{7}{18}\\
11) \dfrac{-3}{4}$

Giải thích các bước giải:

 $1)
\dfrac{15}{34}+\dfrac{7}{21}+\dfrac{19}{34}-\dfrac{20}{15}\\
=\dfrac{15}{34}+\dfrac{19}{34}+\dfrac{1}{3}-\dfrac{4}{3}\\
=\dfrac{34}{34}+\dfrac{-3}{3}\\
=1-1=0\\
2) 2\dfrac{5}{6}+\dfrac{1}{6}:\dfrac{-5}{8}\\
=\dfrac{17}{6}+\dfrac{1}{6}.\dfrac{-8}{5}\\
=\dfrac{17}{6}-\dfrac{4}{15}\\
=\dfrac{85}{30}-\dfrac{8}{30}\\
=\dfrac{77}{30}\\
3) 3-\dfrac{3}{2}+\dfrac{1}{4}-1\dfrac{1}{5}\\
=\dfrac{60}{20}-\dfrac{30}{20}+\dfrac{5}{20}-\dfrac{6}{5}\\
=\dfrac{35}{20}-\dfrac{24}{30}\\
=\dfrac{11}{20}\\
4)
5^3:125+2^4:4\\
=5^3:5^3+2^4:2^2\\
=1+2^2\\
=5\\
5)
23\dfrac{1}{4}:\dfrac{7}{5}-13\dfrac{1}{4}:\dfrac{7}{5}\\
=23\dfrac{1}{4}.\dfrac{5}{7}-13\dfrac{1}{4}.\dfrac{5}{7}\\
=\left ( 23\dfrac{1}{4}-13\dfrac{1}{4} \right ).\dfrac{5}{7}\\
=\left ( 23-13+\dfrac{1}{4}-\dfrac{1}{4} \right ).\dfrac{5}{7}\\
=10.\dfrac{5}{7}\\
=\dfrac{50}{7}\\
6) 12\dfrac{1}{5}.\dfrac{4}{5}-22\dfrac{1}{5}.\dfrac{4}{5}\\
=\dfrac{4}{5}.\left ( 12\dfrac{1}{5}-22\dfrac{1}{5} \right )\\
=\dfrac{4}{5}.\left ( 12-22+\dfrac{1}{5}-\dfrac{1}{5} \right )\\
=\dfrac{4}{5}.(-10)\\
=-8\\
7) (-2)^2+\sqrt{49}-\sqrt{16}+\sqrt{25}\\
=4+7-4+5\\
=12\\
8)
\dfrac{4}{5}-\left ( \dfrac{-1}{2} \right )^2\\
=\dfrac{4}{5}-\dfrac{1}{4}\\
=\dfrac{16}{20}-\dfrac{5}{20}\\
=\dfrac{11}{20}\\
9) 5-\left ( -\dfrac{5}{7} \right )^0+\left ( \dfrac{1}{3} \right )^2:3\\
=5-1+\left (\dfrac{1}{3}  \right )^2.\dfrac{1}{3}\\
=4+\left (\dfrac{1}{3}  \right )^3\\
=4+\dfrac{1}{27}\\
=\dfrac{108}{27}+\dfrac{1}{27}\\
=\dfrac{109}{27}\\
10) \dfrac{2}{9}.\left ( \dfrac{5}{2}-\dfrac{3}{4} \right )\\
=\dfrac{2}{9}.\left ( \dfrac{10}{4}-\dfrac{3}{4} \right )\\
=\dfrac{2}{9}.\dfrac{7}{4}\\
=\dfrac{7}{18}\\
11) 16.\left ( -\dfrac{1}{4} \right )^3-\dfrac{1}{2}\\
=16.\dfrac{-1}{64}-\dfrac{1}{2}\\
=\dfrac{-1}{4}-\dfrac{1}{2}\\
=\dfrac{-1}{4}-\dfrac{2}{4}\\
=\dfrac{-3}{4}$