Bài 4:
1. -$\frac{-4}{30}$-$\frac{-9}{30}$ =$\frac{1}{6}$
2. $\frac{-1}{8}$ - $\frac{1}{120}$ = $\frac{-15}{120}$ - $\frac{1}{120}$ =$\frac{-2}{15}$
3. 2-$\frac{4}{5}$ = $\frac{10}{5}$ -$\frac{4}{5}$=$\frac{6}{5}$
4. $\frac{1}{-2}$ -$\frac{-13}{16}$ -$\frac{7}{8}$ = $\frac{-8}{16}$ - $\frac{-13}{16}$-$\frac{14}{16}$ =[ $\frac{-8}{16}$ - $\frac{-13}{16}$ ]- $\frac{14}{16}$ = $\frac{5}{16}$ - $\frac{14}{16}$= $\frac{-9}{16}$
5. $\frac{3}{4}$ +$\frac{-1}{3}$ -$\frac{-5}{18}$ = $\frac{27}{36}$ - $\frac{-12}{36}$ -$\frac{-10}{36}$ =$\frac{39}{36}$ -$\frac{-10}{36}$ = $\frac{49}{36}$
6. $\frac{-3}{4}$ -$\frac{1}{4}$ + $\frac{-1}{2}$ = $\frac{-3}{4}$-$\frac{1}{4}$+$\frac{-2}{4}$ =$\frac{-3}{2}$
7. $\frac{3}{8}$- ($\frac{3}{4}$ - $\frac{1}{2}$ )= $\frac{3}{8}$-($\frac{6}{8}$ - $\frac{4}{8}$ )=$\frac{3}{8}$- $\frac{2}{8 }$ =$\frac{1}{8}$
8,$\frac{1}{10}$ -($\frac{-1}{12}$ + $\frac{-1}{15}$) = $\frac{6}{60}$ -($\frac{-5}{61}$ -$\frac{-4}{60}$) = $\frac{7}{60}$
9.Mẫu to quá ah :<
Bài 2:
A=$\frac{-5}{9}$ - $\frac{-3}{5}$ - $\frac{1}{9}$ - $\frac{-2}{5}$
⇒ A=($\frac{-5}{9}$-$\frac{1}{9}$)-(-$\frac{3}{5}$ + $\frac{2}{5}$)
⇒ A=($\frac{-5}{9}$ -$\frac{1}{9}$)-($\frac{-3}{5}$+$\frac{2}{5}$)
⇒A=$\frac{4}{9}$ -$\frac{-1}{5}$ =$\frac{11}{45}$
B=$\frac{3}{8}$ + $\frac{-1}{6}$ - $\frac{-1}{3}$ - $\frac{-1}{8}$
⇒$\frac{3}{8}$+ $\frac{-1}{6}$-$\frac{-1}{3}$- $\frac{-1}{8}$
⇒B= ($\frac{3}{8}$- $\frac{-1}{8}$)-($\frac{-1}{3}$ -$\frac{-1}{6}$)
⇒B=$\frac{1}{3}$
C= $\frac{-13}{-26}$ +$\frac{1}{-3}$- $\frac{-1}{2}$-$\frac{7}{21}$
⇒ $\frac{1}{2}$ + $\frac{-1}{3}$- $\frac{-1}{2}$- $\frac{-1}{3}$
⇒ C = [$\frac{1}{2}$-(- $\frac{1}{2}$]+[$\frac{-1}{3}$-$\frac{-1}{3}$]
⇒ C=1
D=$\frac{27}{23}$- $\frac{-5}{21}$- $\frac{-24}{23}$- $\frac{16}{-21}$ -$\frac{1}{-19}$
D=[$\frac{27}{23}$- $\frac{24}{23}$] -[$\frac{-5}{21}$+ $\frac{-16}{21}$- $\frac{1}{19}$
D=$\frac{17}{9}$
