`a)` `\sqrt{12} + \sqrt{27} - \sqrt{48} = 2\sqrt{3} + 3\sqrt{3} - 4\sqrt{3}`
`= \sqrt{3}( 2 + 3 - 4 )`
`= \sqrt{3}`
`b) \sqrt{8} - \sqrt{18} + 2\sqrt{32} = 2\sqrt{2} - 3\sqrt{2} + 2 . 4\sqrt{2}`
`= 2\sqrt{2} - 3\sqrt{2} + 8\sqrt{2}`
`= \sqrt{2}( 2 - 3 + 8 )`
`= 7\sqrt{2}`
`c) \sqrt{5} ( \sqrt{20} - \sqrt{5} ) + 1 = \sqrt{100} - \sqrt{25} + 1`
` = 10 - 5 + 1`
` = 6`
`d)` `\sqrt{(\sqrt{5} - 1)²} - \sqrt{5} = | \sqrt{5} - 1| - \sqrt{5}`
`= \sqrt{5} -1 - \sqrt{5}`
`= -1`
