3x-12x^3=3x(1-4x^2)=3x(1+2x)(1-2x)x^2(x-y)+(y-x)=(x-y)(x^2-1)=(x-y)(x+1)(x-1)-a^4-49b^2+14a^2b=-(a^4-14a^2b+49b^2)=-(a^2-7b)^2a^2(m-n)+b^2(n-m)=(m-n)(a^2-b^2)=(m-n)(a+b)(a-b)16(a-1)^2-(a+2)^2=[4(a-1)]...