[tex]1) \: 2 \times ( 5 \sqrt{3} + 3 \sqrt{2} ) - 10 \sqrt{3} = \\ 10 \sqrt{3} + 6 \sqrt{2} - 10 \sqrt{3} = 6 \sqrt{2} [/tex]
cred ca la 2 e incomplet,mai uita te o data si spune mi
[tex]3) \: 2 \sqrt{7} \times (3 - \sqrt{3} ) + 2 \times (4 + \sqrt{21} ) - 6 \sqrt{7} = 6 \sqrt{7} - 2 \sqrt{21} + 8 + 2 \sqrt{21} - 6 \sqrt{7} = 8[/tex]
[tex]4) \: 18 \sqrt{147} \div ( - 3 \sqrt{3} ) \div ( - 21) = \\ 18 \times 7 \sqrt{3 } \div ( - 3 \sqrt{3} ) \div ( - 21) = \\ 126 \sqrt{3} \div ( - 3 \sqrt{3} ) \div ( - 21) = \\ - 42 \sqrt{3} \div ( - 21) = 2 \sqrt{3} [/tex]