1)
-4x⁴+26x³-12x²=-2x²(2x²-13x+6)
Δ=169-48=121
√Δ=11
x₁=(13-11)/4=1/2
x₂=(13+11)/4=6
-2x²(2(x-1/2)(x-6)
2)
x³-x²-4x+4=x²(x-1)-4(x-1)=(x-1)(x²-4)=(x-1)(x-2)(x+2)
3)
x⁵-2x⁴+7x³+8x²-16x+56=x³(x²-2x+7)+8(x²-2x+7)=(x²-2x+7)(x³+8)=
=(x²-2x+7)(x+2)(x²-2x+4)