x³-6x²y+9xy²-6y³=(x²+a₀xy+a₁y²)(x+a₂y)-x²y
=x³+(a₂+a₀)x²y+(a₀·a₂+a₁)xy²+a₁·a₂y³-x²y
=x³+(a₀+a₂-1)x²y+(a₀·a₂+a₁)xy²+a₁·a₂y³
⇒ a₀+a₂-1=-6
a₀·a₂+a₁=9
a₁·a₂=-6 ;
⇒ a₀=-5-a₂
a₁=-6/a₂
(-5-a₂)a₂-6/a₂=9;
⇒ a₂³+5a₂²+9a₂+6=0
(a₂+1)(a₂+2)(a₂+3)-a₂(a₂+2)=0
(a₂+2)[(a₂+1)(a₂+3)-a₂]=0
(a₂+2)(a₂²+3a₂+3)=0
(a₂+2)[(a₂+3/2)²+3/4]=0
a₂=-2;
a₀=-5-a₂=-3
a₁=-6/a₂=3