x²-6xy+9y²-1=(x²-6xy+9y²)-1=(x-3y)²-1²=[(x-3y)+1][(x-3y)-1]=(x-3y+1)(x-3y-1)am-an-m²+n²=(am-an)-(m²-n²)=a(m-n)-(m+n)(m-n)=(m-n)[a-(m+n)]=(m-n)(a-m-n)2...