Ответ:

1)

[tex] \sqrt{7 \times 3} + \sqrt{ 3} = \sqrt{3} ( \sqrt{7} + 1)[/tex]

2)

[tex]5 + \sqrt{15} - \sqrt{5} = \sqrt{5 \times 5} + \sqrt{5 \times 3} - \sqrt{5} = \sqrt{5} ( \sqrt{5} + \sqrt{3} - 1)[/tex]

3)

[tex] \sqrt{15} - \sqrt{3} = \sqrt{5 \times 3} - \sqrt{3} = \sqrt{3} ( \sqrt{5} - 1)[/tex]

4)

[tex] \sqrt{21} + \sqrt{14} + \sqrt{7} = \sqrt{7 \times 3} + \sqrt{7 \times 2} + \sqrt{7} = \sqrt{7} ( \sqrt{3} + \sqrt{2} + 1)[/tex]

5)

[tex]3 + \sqrt{6} = \sqrt{3 \times 3} + \sqrt{3 \times 2} = \sqrt{3} ( \sqrt{3} + \sqrt{2} )[/tex]

6)

[tex] \sqrt{7} + 7 - \sqrt{14} = \sqrt{7} + \sqrt{7 \times 7} - \sqrt{7 \times 2} = \sqrt{7} (1 + \sqrt{7} - \sqrt{2} )[/tex]