y2=20xy^{2}=20 xy2=20x
9x2+16y2=1449 x^{2}+16 y^{2}=1449x2+16y2=144
x25−y24=1\frac{x^{2}}{5}-\frac{y^{2}}{4}=15x2−4y2=1
x2+y2=25x^{2}+y^{2}=25x2+y2=25
y2−x2=25y^{2}-x^{2}=25y2−x2=25