3,
`\sqrt{9-4\sqrt{5}}-\sqrt{9+4\sqrt{5}}`
`=\sqrt{5-2*2*\sqrt{5}+4}-\sqrt{5+2*2*\sqrt{5}+4}`
`=\sqrt{(\sqrt{5}-2)^2}-\sqrt{(\sqrt{5}+2)^2`
`=\sqrt{5}-2-\sqrt{5}-2=-4`
5,
`\sqrt{94-42\sqrt{5}}-\sqrt{94+42\sqrt{5}}`
`=\sqrt{49-2*7*3\sqrt{5}+(3\sqrt[5])^2}-\sqrt{49+2*7*3\sqrt[5]+(3\sqrt[5])^2`
`=\sqrt{(7-3\sqrt[5])^2}-\sqrt{(7+3\sqrt{5})^2}`
`=7-3\sqrt{5]-7-3\sqrt{5]=-6\sqrt[5]`
6,
`\sqrt{5\sqrt[3]+5\sqrt[48-10\sqrt[7+4\sqrt[3]]]]`
`=\sqrt[5\sqrt[3]+5\sqrt[48-10\sqrt[4+2*2*\sqrt[3]+(\sqrt[3])^2`
`=\sqrt[5\sqrt[3]+5\sqrt[48-10\sqrt[(2+\sqrt[3])^2`
`=\sqrt[5\sqrt[3]+5\sqrt[48-10(2+\sqrt[3])`
`=\sqrt[5\sqrt[3]+5\sqrt[48-20-10\sqrt[3]`
`=\sqrt[5\sqrt[3]+5\sqrt[28-10\sqrt[3]`
`=\sqrt[5\sqrt[3]+5\sqrt[25-2*5\sqrt[3]+(\sqrt[3])^2`
`=\sqrt[5\sqrt[3]+5\sqrt[(5-\sqrt[3])^2`
`=\sqrt[5\sqrt[3]+5(5-\sqrt[3])`
`=\sqrt[5\sqrt[3]+25-5\sqrt[3]`
`=\sqrt[25]=5`
