因式分解（1）:x的4次方+2x的3次方-3x的2次方-4x+4 （2）：2x的4次方+x的3次方+7x的2次方+4x-

x^4+2x^3-3x^2-4x+4
=x^2(x^2+2x-3)-4(x-1)
=x^2(x+3)(x-1)-4(x-1)
=(x-1)[x^2(x+3)-4]
=(x-1)(x^3+3x^2-4)
=(x-1)(x^3-x^2+4x^2-4)
=(x-1)[x^2(x-1)+4(x^2-1)]
=(x-1)[x^2(x-1)+4(x+1)(x-1)]
=(x-1)^2[x^2+4(x+1)]
=(x-1)^2(x^2+4x+4)
=(x-1)^2(x+2)^2
2x^4+x^3+7x^2+4x-4
=2x^4+x^3-x^2+8x^2+4x-4
=x^2(2x^2+x-1)+4(2x^2+x-1)
=(x^2+4)(2x^2+x-1)
=(x^2+4)(2x-1)(x+1)