16x2+25y2=40016 x^{2}+25 y^{2}=40016x2+25y2=400
16x2−25y2=40016 x^{2}-25 y^{2}=40016x2−25y2=400
9x2−4y2=1449 x^{2}-4 y^{2}=1449x2−4y2=144
4x2−9y2=1444 x^{2}-9 y^{2}=1444x2−9y2=144