(1^2-2^2/1+2)+(2^2-3^2/2+3)+(3^2-4^2/3+4)+.+2006^2-2007^2/2006+2007
=(1+2)(1-2)/(1+2)+(2+3)(2-3)/(2+3)+(3+4)(3-4)/(3+4)+.+(2006+2007)(2006-2007)/(2006+2007)
=(-1)+(-1)+(-1)+.+(-1)
=-2006