$\begin{array}{1 1}\large\frac{9x^2}{343}-\frac{y^2}{49}\normalsize =1\\\large\frac{9x^2}{343}+\frac{y^2}{49}\normalsize =1\\\large\frac{9x^2}{343}+\frac{y^2}{49}\normalsize =-1\\\large\frac{9x^2}{343}-\frac{y^2}{49}\normalsize =-1\end{array} $