（1）
x^4+4x^3+3x^2+4x+2
=(x^4+3x^2+2)+4x^3+4x
=(x^2+1)(x^2+2)+4x(x^2+1)
=(x^2+1)(x^2+4x+2)
(2)
x^4+x^3+x^2+2
=x^4-x^3+x^2+2x^3-2x^2+2x+2x^2-2x+2
=x^2(x^2-x+1)+2x(x^2-x+1)+2(x^2-x+1)
=(x^2-x+1)(x^2+2x+2)