Tính:
a) \(\displaystyle{4 \over 9} - {1 \over 3}\) b) \(\displaystyle{{11} \over 6} - {2 \over 3}\)
c) \(\displaystyle{{12} \over 5} - {4 \over 7}\) d) \(\displaystyle{7 \over 8} - {2 \over 7}\)
a) \(\displaystyle{4 \over 9} - {1 \over 3} = {4 \over 9} - {3 \over 9} = {{4 - 3} \over 9} = {1 \over 9}\)
b) \(\displaystyle{{11} \over 6} - {2 \over 3} = {{11} \over 6} - {4 \over 6} = {{11 - 4} \over 6} = {7 \over 6}\)
c) \(\displaystyle{{12} \over 5} - {4 \over 7} = {{84} \over {35}} - {{20} \over {35}} = {{84 - 20} \over {35}} \displaystyle= {{64} \over {35}}\)
d) \(\displaystyle{7 \over 8} - {2 \over 7} = {{49} \over {56}} - {{16} \over {56}} = {{49 - 16} \over {56}} \displaystyle= {{33} \over {56}}\)
-- Mod Toán lớp 4