hihihi's solution is good, but this one may help you solve the problem quicker and easier
(x+y)2 = x2+2xy+y2
(x-y)2=x2-2xy+y2
As such, when you add them together, you get 2x2+2y2
When you plug in x and y, this equals to 2(2006)+2(2007)=4012+4014=8026