由x^(2n)=2得(x^n)²=2,x^n=±√2 -3x^(3n)-4(-x²)^(2n)=-3(x^n)^3-4(x^n)^4=-3(√2)^3-4(√2)^4或=-3(-√2)^3-4(-√2)^4 即 ±6√2-16,2,
