x2+y2=7x^{2}+y^{2}=7x2+y2=7
y2=4xy^{2}=4 xy2=4x
y2=x2+1y^{2}=x^{2}+1y2=x2+1
x24+y23=1\frac{x^{2}}{4}+\frac{y^{2}}{3}=14x2+3y2=1
None