А)(x-1)(x^2+x+1)-(1+x)(1-x+x^2)=x^3+x^2+x-x^2-x-1-1+x-x^2-x+x^2-x^3=-1-1=-2
б)(a^2-3)(a^4+3a^2+9)+a^4(1-a)(1+a)= a^6+3a^4+9a^2-3a^4-9a^2-27+a^4+a^5-a^5-a^6=a^4-27
в)2p^2(2-p)(p^2+2p+4)-4(p-5)(5+p)=4p4+8p^3+16p^2-2p^5-4p^4-8p^3-20p-4p^2+100+20p=(12p^2-2p^5+100)=2(6p^2-p^5+50)
г)n^5(2+n^2)(n^2-2)-(m-n^3)(m^2+mn^3+n^6)=2n^7-4n^5+n^9-2n^7-m^3-m^2n^3-mn^6+m^2n^3+mn^6+n^9=2n^9-4n^5-m^3