Question

如果a=2008x+2007,b=2008x+2008,c=2008x+2009,那么a^2+b^2+c^2-ab-bc

Answer 1

a^2+b^2+c^2-ab-bc-ac =a(a-b)+b(b-c)+c(c-a) =-a-b+2c =(c-a)+(c-b) =2+1=3