6(x-y)-12(x-y)^2
(a^2-b^3)-5(b^3-a^2)-3k(a^2-b^3)

6(x-y)-12(x-y)^26(x-y)=6x-6y(x-y)²=x²-2xy+y²12(x²-2xy+y²)=12x²-24xy+12y²6x-6y-(12x²-24xy+12y²)=6x-6y-12x²+24xy-12y²2)(a^2-b^3)-5(b^3-a^2)-3k(a^2-b^3)a^2-b^3-(5*b^3-5*a^2)=a^2-b^3-5*b^3+5*a^2-b^3-5*b^3=-6*b^3a^2+5*a^2=6*a^23*(a^2-b^3)=3*a^2-3*b^3(3*a^2-3*b^3)*k=3*a^2*k-3*b^3*k6*a^2-6*b^3-(3*a^2*k-3*b^3*k)=6*a^2-6*b^3-3*a^2*k+3*b^3*k