Quy đồng mẫu số các phân số sau:a)     \(\frac{1}{...

- Hướng dẫn giải

Phương pháp giải:

Tìm mẫu số chung sau đó quy đồng mẫu số các phân số. 

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

\(\frac{12}{35}=\frac{12.2}{35.2}=\frac{24}{70};\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\frac{-3}{5}=\frac{-3.14}{5.14}=\frac{-42}{70};\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\frac{15}{-14}=\frac{15.(-5)}{(-14).(-5)}=\frac{-75}{70}\)