a-b=2010x+2011-(2010x+2012)=-1
a-c=2010x+2011-(2010x+2013)=-2
b-c=2010x+2012-(2010x+2013)=1
2a^2+2b^2+2c^2-2ab-2bc-2ca=（a-b)^2+(a-c)^2+(b-c)^2
=1+4+1=6
a^2+b^2+c^2-ab-bc-ca=6/2=3