=[3(x^4-x^2-2)+7](x^4+X^2-2)
=3(x^4-x^2-2)(x^4+X^2-2)+7(x^4+X^2-2)
=3(x^4-2)^2-x^4+7(x^4+X^2-2)
=3x^8-6x^4+7x^2-2