`a)A=\sqrt{(2-\sqrt{3})^2}+2\sqrt{3}`
`A=2-\sqrt{3}+2\sqrt{3}`
`A=2+\sqrt{3}`
Vậy `A=2+\sqrt{3}`
`b)B=\sqrt{18}-2\sqrt{50}+\sqrt{8}+\sqrt{32}`
`B=3\sqrt{2}-2.5\sqrt{2}+2\sqrt{2}+4\sqrt{2}`
`B=3\sqrt{2}-10\sqrt{2}+2\sqrt{2}+4\sqrt{2}`
`B=-\sqrt{2}`
Vậy `B=-\sqrt{2}`
`c)C=1/(\sqrt{5}+2)-\sqrt{9+4\sqrt{5}}`
`C=(\sqrt{5}-2)/((\sqrt{5}+2)(\sqrt{5}-2))-\sqrt{(\sqrt{5})^2+2.\sqrt{5}.2+2^2}`
`C=(\sqrt{5}-2)/(5-4)-\sqrt{(\sqrt{5}+2)^2}`
`C=(\sqrt{5}-2)/1-(\sqrt{5}+2)`
`C=\sqrt{5}-2-\sqrt{5}-2`
`C=-4`
Vậy `C=-4`
