1) (m+n)^3+(m-n)^3-2m=(m+n+m-n)(m²+2mn+n²-m²+n²+m²-2mn+n²)-2m=2m(m²+2n²-1)
2) (a-b)^3-(c+d)^3-a+b+c+d=(a-b-c-d)(a²-2ab+b²+ac+ad-bc-bd+c²+2cd+d²)-(a-b-c-d)=(a-b-c-d)(a²-2ab+b²+ac+ad-bc-bd+c²+2cd+d²-1)
1) (m+n)^3+(m-n)^3-2m=(m+n+m-n)(m²+2mn+n²-m²+n²+m²-2mn+n²)-2m=2m(m²+2n²-1)
2) (a-b)^3-(c+d)^3-a+b+c+d=(a-b-c-d)(a²-2ab+b²+ac+ad-bc-bd+c²+2cd+d²)-(a-b-c-d)=(a-b-c-d)(a²-2ab+b²+ac+ad-bc-bd+c²+2cd+d²-1)