Đáp án:
Giải thích các bước giải:
1. $\frac{1}{7}$ .$\frac{1}{3}$ +$\frac{1}{7}$ $\frac{1}{2}$ -$\frac{1}{7}$
=$\frac{1}{7}$.($\frac{1}{3}$ +$\frac{1}{2}$ -1)
=$\frac{1}{7}$.($\frac{-1}{6}$
=$\frac{-1}{42}$
2. $\frac{3}{5}$ /$\frac{7}{9}$ +$\frac{3}{5}$. $\frac{2}{9}$ +$\frac{3}{5}$
=$\frac{3}{5}$. ($\frac{7}{9}$ +$\frac{2}{9}$ +1)
=$\frac{3}{5}$ .2
=$\frac{6}{5}$
3. 21.($\frac{1}{7}$- $\frac{1}{5}$+ $\frac{19}{21}$ )
=3-$\frac{21}{5}$ +19
=21-$\frac{21}{5}$
=$\frac{84}{5}$
4. 46.($\frac{1}{2}$- $\frac{7}{23}$- $\frac{27}{46}$ ):$\frac{1}{5}$
=46.$\frac{23-14-27}{46}$:$\frac{1}{5}$
=-18.5=-90
5. 75.($\frac{1}{5}$- $\frac{3}{25}$- $\frac{8}{15}$ ).$\frac{1}{4}$
=75.$\frac{15-9-40}{75}$ .$\frac{1}{4}$
=$\frac{-34}{4}$ =$\frac{-17}{2}$
6. -34.($\frac{1}{17}$- $\frac{5}{34}$ +$\frac{1}{2}$ ):4
=-34.$\frac{2-5+17}{34}$ .$\frac{1}{4}$
=$\frac{-14}{4}$ =$\frac{-7}{2}$
7. 45.($\frac{-3}{5}$- $\frac{8}{15}$ +$\frac{7}{3}$ -$\frac{5}{9}$
=45.$\frac{-27-24+105-25}{45}$
=29
8. ($\frac{11}{12}$- $\frac{8}{3}$+ $\frac{1}{12}$- $\frac{1}{3}$ ):$\frac{2}{3}$
= $\frac{11-32+1-4}{12}$ .$\frac{3}{2}$
=-3
9. ($\frac{7}{15}$- $\frac{7}{5}$ +$\frac{8}{15}$+ $\frac{2}{5}$) :$\frac{189}{2007}$
=$\frac{7-21+8+6}{15}$ .$\frac{223}{21}$
=0
10. (-$\frac{5}{9}$ +$\frac{14}{18}$ -$\frac{4}{9}$ +$\frac{2}{9}$ )+$\frac{1}{2007}$
=$\frac{-10+14+8+4}{18}$+$\frac{1}{2007}$
=$\frac{8}{9}$ +$\frac{1}{2007}$
=$\frac{1784+1}{2007}$
=$\frac{595}{669}$
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