Question

整式的乘法越到后越难,已知a=x+2008,b=x+2007,c=x+2006,求a的二次方+b的二次方+c的二次方-a

Answer 1

a^2+b^2+c^2-ab-bc-ac

=1/2[(a-b)^2+(b-c)^2+(a-c)^2]

=1/2[1^2+1^2+2^2]

=1/2*6

=3