`x^2 - 11 = x^2 - (\sqrt{11})^2 = (x - \sqrt{11})(x + \sqrt{11})`
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`x-5 = (\sqrt{x})^2 - (\sqrt{5})^2= (\sqrt{x} - \sqrt{5})(\sqrt{x} + \sqrt{5})`
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Đặt `A = \sqrt{5 - \sqrt{3} } - \sqrt{5 + \sqrt{3} }`
`=> A^2 = (\sqrt{5 - \sqrt{3} } - \sqrt{5 + \sqrt{3} })^2`
`=> A^2 = 5 - \sqrt{3} + 5 + \sqrt{3} - 2 . \sqrt{ (5 -\sqrt{3})(5 + \sqrt{3}) }`
`=> A^2 = 10 - 2 . \sqrt{22}`
`=> A = -\sqrt{10 - 2 \sqrt{22} }` (do `A<0`)