a) 3/4 ; 5/7 và 8/3
3/4 = 63/84
5/7 = 60/84
8/3 = 224/84
b) 5/8 ; 8/13 và 13/17
5/8 = 1105/1768
8/13 = 1088/1768
13/17 = 2496/1768
Chúc em học giỏi !
=>BCNN=84 =>BCNN=1768
\(\frac{3}{4}=\frac{3.21}{4.21}=\frac{63}{84}\) \(\frac{5}{8}=\frac{5.221}{8.221}=\frac{1105}{884}\)
\(\frac{5}{7}=\frac{5.12}{7.12}=\frac{60}{84}\) \(\frac{8}{13}=\frac{8.68}{13.68}=\frac{544}{884}\)
\(\frac{8}{3}=\frac{8.28}{3.28}=\frac{224}{84}\) \(\frac{13}{17}=\frac{13.52}{17.52}=\frac{676}{884}\)