已知a=-2008,b=2007,c=-2006,求a^2+b^2+c^2+ab+bc-ac的值

“凌君婕”您好,很高兴为您解答!
2(A^2+B^2+C^2+AB+BC-AC)=(A^2+2AB+B^2)+(B^2+2BC+C^2))+(A^2-AC+C^2)
=(A+B)^2+(B+C)^2+(A-C)^2
=1+1+4=6
A^2+B^2+C^2+AB+BC-AC=3
2a^n-50a^n+2
=2a^n(1-25^n)
=2a^n(1-5a)(1+5a)