Đáp án:

 $b1:
\dfrac{67}{10}\\
\dfrac{-9}{10}\\
\dfrac{25}{14}\\
\dfrac{-19}{168}\\
\dfrac{-19}{36}\\
\dfrac{-7}{156}\\
B2:
a) -10\\
b) \dfrac{2}{9}\\
c) \dfrac{-17}{57}\\
d) 2002\\
e) -5\\
g) \dfrac{-5}{14}\\
k) 0$

Giải thích các bước giải:

 $b1:
6,5 - \dfrac{-1}{5}=\dfrac{13}{2}+\dfrac{1}{5}=\dfrac{65}{10}+\dfrac{2}{10}=\dfrac{67}{10}\\
\dfrac{2}{5} + \dfrac{-4}{5}+\dfrac{-1}{2}=\dfrac{-2}{5}-\dfrac{1}{2}=\dfrac{-4}{10}-\dfrac{5}{10}=\dfrac{-9}{10}\\
\dfrac{-15}{4} : \dfrac{21}{-10}=\dfrac{-15}{4}.\dfrac{-10}{21}=\dfrac{25}{14}\\
\dfrac{-1}{24} + \dfrac{-1}{14}=\dfrac{-7}{168}-\dfrac{12}{168}=\dfrac{-19}{168}\\
\dfrac{-1}{9} - \dfrac{5}{12}=\dfrac{-4}{36}-\dfrac{15}{36}=\dfrac{-19}{36}\\
( \dfrac{-1}{39} + \dfrac{-1}{52}=\dfrac{-4}{156}-\dfrac{3}{156}=\dfrac{-7}{156}\\$
$B2:
a) \dfrac{-7}{15} . \dfrac{5}{8} . \dfrac{15}{-7 } . (-16)=\dfrac{-7}{15}.\dfrac{15}{-7}.\dfrac{5}{8}.(-16)=-10\\
b) \dfrac{-1}{3} . \dfrac{-15}{17} . \dfrac{34}{45}=\dfrac{5}{17}.\dfrac{34}{45}=\dfrac{2}{9}\\
c) \dfrac{-5}{6} . \dfrac{4}{19} + \dfrac{-7}{12} . \dfrac{4}{19}=\dfrac{4}{19}.\left ( \dfrac{-5}{6}-\dfrac{7}{12} \right )\\
=\dfrac{4}{19}.\left ( \dfrac{-10}{12}-\dfrac{7}{12} \right )\\
=\dfrac{4}{19}.\dfrac{-17}{12}\\
=\dfrac{-17}{57}\\
d) (2008 - \dfrac{2}{135} + \dfrac{1}{50} ) - (1-\dfrac{7}{135} + \dfrac{4}{50} ) - (5+ \dfrac{5}{135} + \dfrac{-3}{50})\\
=2008-\dfrac{2}{135}+\dfrac{1}{50}-1+\dfrac{7}{135}-\dfrac{4}{50}-5-\dfrac{5}{135}+\dfrac{3}{50}\\
=(2008-1-5)+\left ( \dfrac{-2}{135}+\dfrac{7}{135}-\dfrac{5}{135} \right )+\left ( \dfrac{1}{50}-\dfrac{4}{50}+\dfrac{3}{50} \right )\\
=2002+\dfrac{0}{135}+\dfrac{0}{50}\\
=2002\\
e) \dfrac{-24}{11}  + \dfrac{-19} { 13} + \dfrac{2}{11} + \dfrac{-20}{13}\\
=\dfrac{-24}{11}+\dfrac{2}{11}-\dfrac{19}{13}-\dfrac{20}{13}\\
=\dfrac{-22}{11}-\dfrac{39}{13}\\
=-2-3\\
=-5\\
g) \dfrac{-3}{7} . \dfrac{5}{11} + \dfrac{-5}{14} . \dfrac{5}{11}\\
=\dfrac{5}{11}.\left ( \dfrac{-3}{7}-\dfrac{5}{14} \right )\\
=\dfrac{5}{11}.\left ( \dfrac{-6}{14}-\dfrac{5}{14} \right )\\
=\dfrac{5}{11}.\dfrac{-11}{14}\\
=\dfrac{-5}{14}\\
k) ( \dfrac{-5}{6} + \dfrac{2}{5} ) : \dfrac{3}{8} + (\dfrac{4}{5} - \dfrac{11}{30}) : \dfrac{3}{8}\\
=\left ( \dfrac{-5}{6}+\dfrac{2}{5}+\dfrac{4}{5}-\dfrac{11}{30} \right ):\dfrac{3}{8}\\
=\left ( \dfrac{-5}{6}+\dfrac{6}{5}-\dfrac{11}{30} \right ):\dfrac{3}{8}\\
=\left ( \dfrac{-25}{30}+\dfrac{36}{30}-\dfrac{11}{30} \right ):\dfrac{3}{8}\\
=\dfrac{0}{30}:\dfrac{3}{8}=0$

Đáp án:

Giải thích các bước giải:

 Bài 1:

a,6,5-(-1/5)

=$\frac{13}{2}$+$\frac{1}{5}$ 

=$\frac{65}{10}$+$\frac{2}{10}$=$\frac{67}{10}$ 

b,$\frac{2}{5}$-$\frac{4}{5}$+$\frac{-1}{2}$ 

=$\frac{4}{10}$-$\frac{5}{10}$ 

c,$\frac{-15}{4}$:$\frac{21}{10}$=$\frac{-15}{4}$.$\frac{-10}{21}$=$\frac{25}{14}$

d,$\frac{-1}{24}$+$\frac{-1}{14}$=$\frac{-14}{336}$+$\frac{-24}{336}$=$\frac{-38}{336}$ 

e,$\frac{-1}{9}$-$\frac{5}{12}$=$\frac{-12}{108}$-$\frac{45}{108}$=$\frac{-33}{108}$ 

g,$\frac{-1}{39}$+$\frac{-1}{52}$=$\frac{-52}{2028}$+$\frac{-39}{2028}$ \=$\frac{-91}{2028}$ 

Bài 2:

a,$\frac{-7}{15}$.$\frac{5}{8}$.$\frac{15}{-7}$.16=($\frac{-7}{15}$.$\frac{15}{-7}$).$\frac{5.-16}{8}$ 

=-1.-10

=10

b,$\frac{-1}{3}$.$\frac{-15}{17}$.$\frac{34}{45}$=$\frac{-1}{3}$.$\frac{-1}{1}$.$\frac{2}{3}$=$\frac{1}{3}$.$\frac{2}{3}$=$\frac{3}{9}$=$\frac{1}{3}$ 

c,$\frac{-5}{6}$.$\frac{4}{19}$+$\frac{-7}{12}$.$\frac{4}{19}$=$\frac{4}{9}$.($\frac{-10}{12}$+ $\frac{-7}{12}$)=$\frac{4}{9}$.$\frac{-17}{12}$= $\frac{-17}{57}$ 

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