1.(a²+a+1)(a²-a+1) =[(a²+1)+a][(a²+1)-a]=(a²+1)²-a²=a^4+2a²+1-a²=a^4+a²+12.(x-y)(x+y)+(3x-2y)(2x+y)-x(6x-y)=x²-y²+6x²-xy-2y²-6x²+xy=x²-3y²