請問這數如何運算

√[X+3√(X+1)] - 3 = 0
√[X+3√(X+1)] = 3
X+3√(X+1) = 9
3√(X+1) = 9-X
9(X+1) = X2-18X+81
X2-27X+72 = 0
(X-3)(X-24) = 0
X = 3 或 X = 24

驗算：
√[3+3√(3+1)] - 3
= √[3+3(2)] - 3
= 3 - 3
= 0

√[24+3√(24+1)] - 3
= √[24+3(5)] - 3
= √39 - 3
≠ 0

∴ X=3


√[20+√(X-2)] - √(3X-56) = 0
√[20+√(X-2)] = √(3X-56)
20+√(X-2) = 3X-56
√(X-2) = 3X-76
X-2 = 9X2-456X-5776
9X2-457X-5778 = 0
(X-27)(9X-214) = 0
X = 27 或 X = 214/9

驗算：
√[20+√(27-2)] - √[3(27)-56]
= √(20+5) - √25
= 5 - 5
= 0

√[20+√(214/9 - 2)] - √[3(214/9)-56]
= √[20+√(214/9 - 2)] - √[3(214/9)-56]
= √(20+√196) - √[(214/3)-56]
= √(20+14) - √(46/3)
= √34 - √(46/3)
≠ 0

∴ X=27