Pasos:
[tex]-x^2+2x-1\\Factorizar -1:-(x^2-2x+1)\\=-(x^2-2x+1)\\Factorizar: x^2-2x+1:(x-1)(x-1)\\=-(x-1)(x-1)\\[/tex]
Aplicar las leyes de los exponentes: [tex]aa=a^{2}[/tex]
[tex]=-(x-1)^{2}[/tex]