Đáp án:
Giải thích các bước giải:
$S_{1}=1+(-2)+3+(-4)+...+(-2014)+2015\\\Leftrightarrow S_{1}=(1+3+...+2015)-(2+4+...+2014)\\\Leftrightarrow S_{1}=2((\frac{\frac{2015+1}{2})^2}{2}+\frac{\frac{2015+1}{2}}{2})-\frac{2015+1}{2}-2(\frac{(\frac{2014}{2})^2}{2}+\frac{\frac{2014}{2}}{2})\\=3022\\S_{2}=-2+4-6+...-2014+2016\\\Leftrightarrow S_{2}=(4+8+...+2016)-(2+6+...+2014)\\\Leftrightarrow S_{2}=4(\frac{(\frac{2016}{4})^2}{2}+\frac{\frac{2016}{4}}{2})-4(\frac{(\frac{2014+2}{4})^2}{2}+\frac{\frac{2014+2}{2}}{2})-2\frac{2014+2}{2}\\\Leftrightarrow S_{2}=-518242934160$