$\begin{array}{1 1}\large\frac{x^2}{25}+\large\frac{y^2}{9}=1 \\ \large\frac{x^2}{9}+\large\frac{y^2}{25}=1 \\ \large\frac{x^2}{25}+\large\frac{y^2}{16}=1 \\\large\frac{x^2}{16}+\large\frac{y^2}{9}=1\end{array} $