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a)\(\dfrac{3}{7}=\dfrac{3.8}{7.8}=\dfrac{24}{56};\dfrac{5}{8}=\dfrac{5.7}{8.7}=\dfrac{35}{56}\)
b)\(\dfrac{7}{10}=\dfrac{7.2}{10.2}=\dfrac{14}{20};\dfrac{3}{20}\)
c)\(\dfrac{9}{20}=\dfrac{9.9}{20.9}=\dfrac{81}{180};\dfrac{2}{9}=\dfrac{2.20}{9.20}=\dfrac{40}{180}\)
Lời giải:
a. $\frac{5}{9}=\frac{5\times 2}{9\times 2}=\frac{10}{18}$
b. $\frac{9}{20}=\frac{9\times 3}{20\times 3}=\frac{27}{60}$
Bài 1:
a)
\(\dfrac{1}{2}=\dfrac{1\times6}{2\times6}=\dfrac{6}{12}\)
\(\dfrac{2}{3}=\dfrac{2\times4}{3\times4}=\dfrac{8}{12}\)
\(\dfrac{3}{4}=\dfrac{3\times3}{4\times3}=\dfrac{9}{12}\)
b)
\(\dfrac{1}{3}=\dfrac{1\times15}{3\times15}=\dfrac{15}{45}\)
\(\dfrac{2}{15}=\dfrac{2\times3}{15\times3}=\dfrac{6}{45}\)
\(\dfrac{4}{45}\) (giữ nguyên)
c)
\(\dfrac{1}{8}=\dfrac{1\times3}{8\times3}=\dfrac{3}{24}\)
\(\dfrac{2}{3}=\dfrac{2\times8}{3\times8}=\dfrac{16}{24}\)
\(\dfrac{5}{2}=\dfrac{5\times12}{2\times12}=\dfrac{60}{24}\)
d)
\(\dfrac{2}{7}=\dfrac{2\times4}{7\times4}=\dfrac{8}{28}\)
\(\dfrac{9}{4}=\dfrac{9\times7}{4\times7}=\dfrac{63}{28}\)
\(\dfrac{5}{28}\) (giữ nguyên)
Bài 2:
a)
\(4=\dfrac{4}{1}=\dfrac{4\times12}{1\times12}=\dfrac{48}{12}\)
\(\dfrac{9}{4}=\dfrac{9\times3}{4\times3}=\dfrac{27}{12}\)
b)
\(\dfrac{5}{8}=\dfrac{5\times30}{8\times30}=\dfrac{150}{240}\)
\(\dfrac{25}{30}=\dfrac{5}{6}=\dfrac{5\times40}{6\times40}=\dfrac{200}{240}\)
\(2=\dfrac{2}{1}=\dfrac{2\times240}{1\times240}=\dfrac{480}{240}\).
a: \(\dfrac{5}{7}=\dfrac{5\cdot11}{7\cdot11}=\dfrac{55}{77}\)
\(\dfrac{9}{11}=\dfrac{9\cdot7}{11\cdot7}=\dfrac{63}{77}\)
b: \(\dfrac{36}{42}=\dfrac{6}{7}=\dfrac{6\cdot9}{7\cdot9}=\dfrac{54}{63}\)
\(-\dfrac{12}{54}=\dfrac{-2}{9}=\dfrac{-2\cdot7}{9\cdot7}=-\dfrac{14}{63}\)
c: \(\dfrac{-11}{30}=\dfrac{-11\cdot4}{30\cdot4}=\dfrac{-44}{120}\)
\(\dfrac{-17}{-40}=\dfrac{17}{40}=\dfrac{17\cdot3}{40\cdot3}=\dfrac{51}{120}\)
d: \(\dfrac{36}{42}=\dfrac{6}{7}=\dfrac{6\cdot3}{7\cdot3}=\dfrac{18}{21}\)
\(\dfrac{-12}{36}=\dfrac{-1}{3}=\dfrac{-1\cdot7}{3\cdot7}=\dfrac{-7}{21}\)
a)
MSC: 35
\(\dfrac{4}{7}=\dfrac{4\times5}{7\times5}=\dfrac{20}{35}\)
\(\dfrac{28}{35}\) giữ nguyên
b)
MSC: 100
\(\dfrac{13}{20}=\dfrac{13\times5}{20\times5}=\dfrac{65}{100}\)
c)
MSC: 24
\(\dfrac{5}{6}=\dfrac{5\times4}{6\times4}=\dfrac{20}{24}\)
\(\dfrac{9}{8}=\dfrac{9\times3}{8\times3}=\dfrac{27}{24}\)
a, 4/7 và 28/35
ta có :
4/7=20/35
28/35
b13/20 và 32/100
ta có :
13/20=65/100
32/100
c,5/6,9/8 và 11/24
ta có :
5/6=20/24
9/8=27/24
11/24
a: 3/8=36/96
5/12=40/96
b: -2/9=-24/108
-5/12=-45/108
c: -3/16=-63/336
-5/24=-70/336
-21/56=-126/336
a) \(\dfrac{3}{4}=\dfrac{3\times4}{4\times4}=\dfrac{12}{16}\)
b) \(\dfrac{1}{3}=\dfrac{1\times3}{3\times3}=\dfrac{3}{9}\)
c) \(\dfrac{5}{6}=\dfrac{5\times3}{6\times3}=\dfrac{15}{18}\)
a: -9/20=-36/320
17/320=17/320
b: -7/10=-231/330
1/33=10/330
c: -5/15=-1/3=-140/420
3/20=63/420
9/70=54/420
d: 10/42=5/21=20/84
-3/28=-9/84
-55/132=-5/12=-35/84