4（2x²-x+1）（x²-2x+3）-（3x²-3x+4）²
=4(2x^4-4x³+6x²-x³+2x²-3x+x²-2x+3)-(9x^4-9x³+12x²-9x³+9x²-12x+12x²-12x+16)
=4(2x^4-5x³+9x²-5x+3)-(9x^4-18x³+33x²-24x+16)
=8x^4-20x³+36x²-20x+12-9x^4+18x³-33x²+24x-16
=-x^4-2x³+3x²+4x-4
=-x²(x²+2x-3)+4(x-1)
=-x²(x+3)(x-1)+4(x-1)
=(x-1)[4-x²(x+3)]