若$\left\{\begin{array}{l}x=1\\ y{\rm=-}1\end{array}\right.$和$\left\{\begin{array}{l}x=3\\ y=5\end{array}\right.$都是方程$ax\text{+}by\text{+}2\text{=}0$的解，试判断$\left\{\begin{array}{l}x=4\\ y=8\end{array}\right.$是否为方程$ax\text{+}by\text{+}2\text{=}0$的又一个解？