Question

Quy đồng mẫu các phân số :

a) \(\frac{-4}{7}\); \(\frac{8}{9}\); \(\frac{-10}{21}\)

b) \(\frac{5}{2^2.3}\); \(\frac{7}{2^3.11}\)

Answer 1

a)MSC: 63. Ta có: \(\frac{-4}{7}\)=\(\frac{-4.9}{7.9}\)=\(\frac{-36}{63}\)          ;            \(\frac{8}{9}\)=\(\frac{8.7}{9.7}\)=\(\frac{56}{63}\)               ;             \(\frac{-10}{21}\)=\(\frac{-10.3}{21.3}\)=\(\frac{-30}{63}\)

b) \(\frac{5}{2^2.3}\)=\(\frac{5}{12}\);\(\frac{7}{2^3.11}\)=\(\frac{7}{88}\)

MSC: 264. Ta có: \(\frac{5}{12}\)=\(\frac{5.22}{12.22}\)=\(\frac{110}{264}\)          ;          \(\frac{7}{88}\)=\(\frac{7.3}{88.3}\)=\(\frac{21}{264}\)