Ответ:

  1. \(2x^2+4x+2=2(x^2+2x+1)=2(x+1)^2\).

  2. \(8n^2-16n+8=8(n^2-2n+1)=8(n-1)^2\).

  3. \(3m^2+3n^2-6mn=3(m^2-2mn+n^2)=3(m-n)^2\).