10.
设\(O\)为原点,向量\(\overrightarrow{O{{Z}_{1}}}\)、\(\overrightarrow{O{{Z}_{2}}}\)分别对应复数\({{z}_{1}}\)、\(z2\),且\({z}_{1}= \dfrac{8}{a+5}+(10-{a}^{2}) \),\({z}_{2}= \dfrac{2}{1-a}+(2a-5) \),\(a∈R \),若\( \overset{¯}{{z}_{1}}+{z}_{2} \)是实数.
\((1)\)求实数\(a\)的值;
\((2)\)求以\( \overset{→}{O{Z}_{1}}, \overset{→}{O{Z}_{2}} \)为邻边的平行四边形的面积.