x⁴-x²+4x-4
x⁴-(x²-4x+4)
x⁴-(x-2)²
(x²-(x-2))(x²+(x-2))
(x²-x+2)(x²+x-2)
(x²-x+2)(x²+2x-x-2)
(x²-x+2)(x(x+2)-(x+2))
(x²-x+2)(x+2)(x-1)
x⁴-x²+4x-4
x⁴-(x²-4x+4)
x⁴-(x-2)²
(x²-(x-2))(x²+(x-2))
(x²-x+2)(x²+x-2)
(x²-x+2)(x²+2x-x-2)
(x²-x+2)(x(x+2)-(x+2))
(x²-x+2)(x+2)(x-1)