Bài 4 (tiết 2):
a) \(\dfrac{17}{20}-\dfrac{6}{20}-\dfrac{9}{20}=\dfrac{17-6-9}{20}=\dfrac{2}{20}=\dfrac{1}{10}\)
b) \(\dfrac{15}{16}-\dfrac{1}{16}-\dfrac{10}{16}=\dfrac{15-1-10}{16}=\dfrac{4}{16}=\dfrac{1}{4}\)
c) \(\dfrac{10}{14}-\dfrac{7}{14}-\dfrac{1}{14}=\dfrac{10-7-1}{14}=\dfrac{2}{14}=\dfrac{1}{7}\)
d) \(\dfrac{20}{22}-\dfrac{9}{22}-\dfrac{3}{22}=\dfrac{20-9-3}{22}=\dfrac{8}{22}=\dfrac{4}{11}\)
bài 3(Tiết 1)
\(\dfrac{3}{12}+\dfrac{3}{12}=\dfrac{3+3}{12}=\dfrac{6}{12}=\dfrac{1}{2}\)
\(\dfrac{5}{6}+\dfrac{4}{6}=\dfrac{5+4}{6}=\dfrac{9}{6}=\dfrac{3}{2}\)
\(\dfrac{8}{9}+\dfrac{1}{9}=\dfrac{8+1}{9}=\dfrac{9}{9}=1\)
\(\dfrac{15}{20}+\dfrac{5}{20}=\dfrac{15+5}{20}=\dfrac{20}{20}=1\)
Bài 3(Tiết 2)
a: \(\dfrac{8}{8}-\dfrac{2}{8}=\dfrac{8-2}{8}=\dfrac{6}{8}=\dfrac{3}{4}\)
b: \(\dfrac{17}{20}-\dfrac{7}{20}=\dfrac{17-7}{20}=\dfrac{10}{20}=\dfrac{1}{2}\)
c: \(\dfrac{8}{15}-\dfrac{3}{15}=\dfrac{8-3}{15}=\dfrac{5}{15}=\dfrac{1}{3}\)
d: \(\dfrac{19}{7}-\dfrac{5}{7}=\dfrac{19-5}{7}=\dfrac{14}{7}=2\)
Bài 4 (tiết 1):
\(\dfrac{4}{8}+\dfrac{2}{8}+\dfrac{1}{8}=\dfrac{4+2+1}{8}=\dfrac{7}{8}\)
\(\dfrac{4}{12}+\dfrac{3}{12}+\dfrac{1}{12}=\dfrac{4+3+1}{12}=\dfrac{8}{12}=\dfrac{2}{3}\)
\(\dfrac{2}{9}+\dfrac{3}{9}+\dfrac{4}{9}=\dfrac{2+3+4}{9}=\dfrac{9}{9}=1\)
\(\dfrac{2}{7}+\dfrac{5}{7}+\dfrac{3}{7}=\dfrac{2+5+3}{7}=\dfrac{10}{7}\)
