a(x)=(x-4)²(x+2)=(x²-8x+16)(x+2)
a(x)=x^3-8x²+16x+2x²-16x+32
a(x)=x³-6x²+32

b(x)=(2-x)(x²+4x+4-12)
b(x)=2x²+8x-16-x³-4x²+8x
b(x)=-x³-2x²+16x-16

b(x)=(2-x)(x+2+V12)(x+2-V12)
b(x)=(2-x)(x+2+2V3)(x+2-2V3)

a(x)=0 ssi x=4 ou x=-2.
b(x)=0 ssi x=2 ou x=-2-2V3 ou x=-2+2V3.

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