Răspuns:
=x²-2ax+a²+x²-4x+(2a)²-x²+6ax-(3a)²=x²-4a²
[tex]\it (x-a)^2+(x-2a)^2+(x-3a)^2=x^2-2ax+a^2+x^2-4ax+4a^2-x^2+6ax-9a^2=\\ \\ =x^2-4a^2[/tex]
