Question 89365


  
Multiply. (a^2 + ab – b^2)(a^2 – 4ab + b^2)

          a^2(a^2-4ab+b^2)+ab(a^2-4ab+b^2)-b^2(a^2-4ab+b^2)
         = a^4-4a^3b+a^2b^2+a^3b-4a^2b^2+ab^3-a^2b^2-4ab^3-b^4
         = a^4-b^4-3a^3b-3ab^3-4a^2b^2