Tính:
a) \(\displaystyle{3 \over 4} - {2 \over 3}\) b) \(\displaystyle{7 \over 5} - {3 \over 7}\)
c) \(\displaystyle{4 \over 3} - {3 \over 5}\) d) \(\displaystyle{{11} \over 3} - {2 \over 5}\)
a) \(\displaystyle{3 \over 4} - {2 \over 3} = {9 \over {12}} - {8 \over {12}} = {1 \over {12}}\)
b) \(\displaystyle{7 \over 5} - {3 \over 7} = {{49} \over {35}} - {{15} \over {35}} = {{34} \over {35}}\)
c) \(\displaystyle{4 \over 3} - {3 \over 5} = {{20} \over {15}} - {9 \over {15}} = {{11} \over {15}}\)
d) \(\displaystyle{{11} \over 3} - {2 \over 5} = {{55} \over {15}} - {6 \over {15}} = {{49} \over {15}}\)
-- Mod Toán lớp 4