Quy đồng mẫu số các phân số sau:
a) \(\frac{1}{3};\,\,\frac{3}{5}\)
b) \(\frac{-1}{2};\,\,\frac{5}{7}\)
c) \(\frac{1}{10};\,\,\frac{-3}{20}\)
d) \(\frac{-5}{9};\,\,\frac{7}{-15}\)
e) \(\frac{-1}{5}\ ;\,\frac{7}{-2}\ ;\ \frac{3}{4}\)
f) \(\frac{12}{35}\ ;\,\frac{-3}{5}\ ;\ \frac{15}{-14}\)
Câu 242893: Quy đồng mẫu số các phân số sau:
a) \(\frac{1}{3};\,\,\frac{3}{5}\)
b) \(\frac{-1}{2};\,\,\frac{5}{7}\)
c) \(\frac{1}{10};\,\,\frac{-3}{20}\)
d) \(\frac{-5}{9};\,\,\frac{7}{-15}\)
e) \(\frac{-1}{5}\ ;\,\frac{7}{-2}\ ;\ \frac{3}{4}\)
f) \(\frac{12}{35}\ ;\,\frac{-3}{5}\ ;\ \frac{15}{-14}\)
Tìm mẫu số chung sau đó quy đồng mẫu số các phân số.
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Giải chi tiết:
a) MSC = 3. 5 = 15
\(\frac{1}{3}=\frac{1.5}{3.5}=\frac{5}{15};\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\frac{3}{5}=\frac{3.3}{5.3}=\frac{9}{15}\)
b) MSC = 2. 7 = 14
\(\frac{-1}{2}=\frac{-1.7}{2.7}=\frac{-7}{14};\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\frac{5}{7}=\frac{5.2}{7.2}=\frac{10}{14}\)
c) MSC = 20
\(\frac{1}{10}=\frac{1.2}{10.2}=\frac{2}{20};\,\,\) \(\frac{-3}{20}\) giữ nguyên
d) MSC = 45
\(\frac{-5}{9}=\frac{-5.5}{9.5}=\frac{-25}{45};\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\frac{7}{-15}=\frac{7.(-3)}{(-15).(-3)}=\frac{-21}{45}\)
e) MSC = 20
\(\frac{-1}{5}=\frac{-1.4}{5.4}=\frac{-4}{20};\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\frac{7}{-2}=\frac{7.(-10)}{(-2).(-10)}=\frac{-70}{20};\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\frac{3}{4}=\frac{3.5}{4.5}=\frac{15}{20}\)
f) MSC =70
\(\frac{12}{35}=\frac{12.2}{35.2}=\frac{24}{70};\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\frac{-3}{5}=\frac{-3.14}{5.14}=\frac{-42}{70};\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\frac{15}{-14}=\frac{15.(-5)}{(-14).(-5)}=\frac{-75}{70}\)
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