`c)` `\sqrt{4-2\sqrt{3}}`
`=\sqrt{3-2\sqrt{5}+1}`
`=\sqrt{(\sqrt{3})^2 -2\sqrt{3}+1}`
`=\sqrt{(\sqrt{3}-1)^2}`
`=|\sqrt{3}-1|=\sqrt{3}-1`
`d)`
`\sqrt{9+4\sqrt{5}}`
`=\sqrt{5+4\sqrt{5}+4}`
`=\sqrt{(\sqrt{5})^2 +2.2\sqrt{5}+4}`
`=\sqrt{(\sqrt{5}+2)^2}`
`=|\sqrt{5}+2|=\sqrt{5}+2`
`e)`
`\sqrt{8-2\sqrt{7}}`
`=\sqrt{7-2\sqrt{7}+1}`
`=\sqrt{(\sqrt{7})^2 -2\sqrt{7}+1}`
`=\sqrt{(\sqrt{7}-1)^2}`
`=|\sqrt{7}-1|=\sqrt{7}-1`