[u]A [b]Surd[/b] is a square root which cannot be reduced to a whole number.[/u] They are [b]Irrational numbers[/b].
[b]E.g
18 = irrational number
= 9 * 2[/b] [i][as the numbers in the root multiply to give 18][/i]
[b] = [u]3 * 2[/u][/b] [i][simplifying what you can][/i]
[i][one thing to note is that one of the numbers of the surd must be able to be square rooted to a whole numbers][/i]
[b]1) [/b]
20 = 45
[u] = 2 * 5[/u]
[b]2) [/b]
4 * 8 = 16 * 3
[u] = 4 * 3[/u]