4x^3-8x^2+4x=4x(x²-2x+1)=4x(x-1)²

　　a^2-2a(b+c)+(b+c)^2=[a-(b+c)]²=(a-b-c)²

　　x^2+3x+2=(x+1)(x+2)

　　m^2-4m+3=(m-1)(m-3)

　　x^2-3xy+2y^2=(x-y)(x-2y)

　　x^2y^2-5x^2y-6x^2=x²(y²-5y-6)=x²(y-6)(y+1)