x^4-3x^2+1
=(x^2)^2-3(x^2)+1
=(x^2)^2-2(x^2)+1-x^2
=(x^2-1)^2-x^2
=(x^2-x-1)(x^2+x-1) 有理数范围止!
=(x-1/2-√5/2)(x-1/2+√5/2)(x+1/2-√5/2)(x+1/2+√5/2) 实数范围内!