a^2b^2c-abc+1/4c;a^2(x-y)+b^2(y-x);

a^2b^2c-abc+1/4c=c(a^2b^2-ab+1/4)=c(ab-1/2)^2;a^2(x-y)+b^2(y-x)=a^2(x-y)-b^2(x-y)=(x-y)(a^2-b^2)=(x-y)(a+b)(a-b)。