6/7 = .../21 = 12/... = .../35
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\(\dfrac{7}{21}+\dfrac{-9}{36}=\dfrac{1}{3}+\dfrac{-1}{4}=\dfrac{4}{12}+\dfrac{-3}{12}=\dfrac{1}{12}\)
\(\dfrac{-12}{18}+\dfrac{-21}{35}=\dfrac{-2}{3}+\dfrac{-3}{5}=\dfrac{-10}{15}+\dfrac{-9}{15}=\dfrac{-19}{15}\)
\(\dfrac{-18}{14}+\dfrac{15}{-21}=\dfrac{-9}{7}+\dfrac{-5}{7}=\dfrac{-14}{7}=-2\)
\(\dfrac{3}{21}+\dfrac{-6}{42}=\dfrac{1}{7}+\dfrac{-1}{7}=0\)
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1)1/6 - - 5/6 = 1/6 + 5/6 = 1
2)6/13 - -14/39 = 6/13 + 14/39= 32/39
3)4/5 - 4/-18 = 4/5 + 4/18= 46/45
4)7/21 - 9/-36 = 7/21 + 9/36 = 7/12
5)-12/18 - -21/35 = -12/18 + 21/35 = -1/15
6)-3/21 - 6/42 = -2/7
7)-18/24 - 15/21 = -41/28
8)1/6 - 2/5 =-7/30
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Mình làm câu này các câu khác tương tự
Mấu chốt làm bài này là đưa về thừa số nguyên tố
\(\frac{12^7.3^{35}.14^{21}}{9^{21}.7^{21}.2^{35}}=\frac{3^7.4^7.3^{35}.2^{21}.7^{21}}{3^{2.21}.7^{21}.2^{35}}=\frac{3^7.2^{2.7}.3^{35}.2^{21}.7^{21}}{3^{2.21}.7^{21}.2^{35}}=\frac{3^7.2^{14}.3^{35}.2^{21}.7^{21}}{3^{42}.7^{21}.2^{35}}=\frac{3^{42}.2^{35}.7^{21}}{3^{42}.7^{21}.2^{35}}=1\)
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\(a,\frac{11}{12}:\frac{7}{24}\cdot\frac{21}{24}=\frac{11\cdot24\cdot7\cdot3}{4\cdot3\cdot7\cdot24}=\frac{11}{4}\)
\(b,\frac{5}{12}:\frac{7}{4}-\frac{25}{18}:\frac{35}{6}=\frac{5\cdot4}{3\cdot4\cdot7}-\frac{5\cdot5\cdot6}{6\cdot3\cdot5\cdot7}=\frac{5}{21}\)
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\(1.a:S;\text{ }b:Đ;\text{ }c:Đ;\text{ }d:S.\)
\(3.a.\dfrac{2}{4};\dfrac{2}{6};\dfrac{4}{6};\dfrac{4}{8};\dfrac{2}{8};\dfrac{6}{8}.\)
\(b.\dfrac{1}{2};\dfrac{1}{3};\dfrac{2}{3};\dfrac{1}{2};\dfrac{1}{4};\dfrac{3}{4}.\)
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a) \(\frac{1}{4}\)
b) \(\frac{2}{7}\)
c) \(\frac{2}{3}\)
6/7 = 18/21 12/7 = 60/35
6/7 = 18/21 = 12/14 = 30/35