x²-√(x²-3x+5)=3x+1
(x²-3x+5)-6=√(x²-3x+5)
令t=√(x²-3x+5) 代入 (t>0)
则t²-6=t
(t-3)(t+2)=0
得t=3 or -2(舍去)
所以√(x²-3x+5)=3
x²-3x+5=9
x²-3x-4=0
(x-4)(x+1)=0
解得x=4 or -1