1)
[tex](2 \sqrt{32} - 4 \sqrt{8} ) \div 7 \sqrt{2} = (2 \sqrt{4 \times 8} - 4 \sqrt{8} ) \div 7 \sqrt{2} = (4 \sqrt{8} - 4 \sqrt{8} ) \div 7 \sqrt{2} = 0 \div 7 \sqrt{2} = 0[/tex]
2)
[tex](5 \sqrt{3} - \sqrt{27} ) \div 2 = (5 \sqrt{3} - \sqrt{9 \times 3} ) \div 2 = (5 \sqrt{3} - 3 \sqrt{3} ) \div 2 = 2 \sqrt{3} \div 2 = \sqrt{3} [/tex]
3)
[tex]( \sqrt{54} - \sqrt{24} ) \div ( \sqrt{27} - \sqrt{12} ) = (3 \sqrt{6} - 2 \sqrt{6} ) \div (3 \sqrt{3} - 2 \sqrt{3} ) = \sqrt{6} \div \sqrt{3} = \sqrt{2} [/tex]
