a.
[tex] \sqrt{45} + \sqrt{20} - \sqrt{125} = \\ 3 \sqrt{5} + 2 \sqrt{5} - 5 \sqrt{5} = \\ 5 \sqrt{5} - 5 \sqrt{5} = \\ = 0[/tex]
b.
[tex] \sqrt{8} + \sqrt{18} - \sqrt{32} = \\ 2 \sqrt{2} + 3 \sqrt{2} - 4 \sqrt{2} = \\ 5 \sqrt{2} - 4 \sqrt{2} = \\ = \sqrt{2} [/tex]
c.
[tex] \sqrt{27} + \sqrt{243} + \sqrt{75} - \sqrt{108} = \\ 3 \sqrt{3} + 9 \sqrt{3} + 5 \sqrt{3} - 6 \sqrt{3} = \\ 12 \sqrt{3} + 5 \sqrt{3} - 6 \sqrt{3} = \\17 \sqrt{3} - 6 \sqrt{3} = 11 \sqrt{3} [/tex]
d.
[tex] \sqrt{72} - \sqrt{98} + \sqrt{128} = \\ 6 \sqrt{2} - 7 \sqrt{2} + 8 \sqrt{2} = \\ - \sqrt{2} + 8 \sqrt{2} = 7 \sqrt{2} [/tex]
