Question 27
Let
$$
\begin{aligned} S_n&=1-2+3-4+\cdots\\ &\quad+(-1)^{n-1}n. \end{aligned}
$$
Here $n=1,$ $2,$ $\ldots.$ Then $S_{17}+S_{33}+S_{50}$ equals:
$$
\begin{aligned} S_n&=1-2+3-4+\cdots\\ &\quad+(-1)^{n-1}n. \end{aligned}
$$
Here $n=1,$ $2,$ $\ldots.$ Then $S_{17}+S_{33}+S_{50}$ equals: