[tex]\displaystyle\\
\text{Voi descompune in factori separat grupul de termeni care }\\
\text{contin puterile lui x si separat grupul celorlalti termeni.}\\\\
x^4-4x^3+4x^2-9y^2+6y-1 =\\\\
=(x^4-4x^3+4x^2)-(9y^2-6y+1) =\\\\
=x^2(x^2-4x+4)-(9y^2-6y+1) =\\\\
=x^2(x-2)^2-(3y-1)^2\\\\
[/tex]