12 - 22 + 32 - 42 + .... + 20152 - 20162 + 20172
= (1 - 2)(1 + 2) + (3 - 4)(3 + 4) + .... + (2015 - 2016)(2015 + 2016) + 20172
= - 1.(1 + 2) - 1(3 + 4) - .... - 1.(2015 + 2016) + 20172
= - 1(1 + 2 + 3 + .... + 2015 + 2016) + 20172
\(=-\frac{2016.2017}{2}+2017\)
= - 2031119