x2+y2=3a2x^{2}+y^{2}=3 a^{2}x2+y2=3a2
2(x2+y2)=a22\left(x^{2}+y^{2}\right)=a^{2}2(x2+y2)=a2
2(x2+y2)=3a22\left(x^{2}+y^{2}\right)=3 a^{2}2(x2+y2)=3a2
3(x2+y2)=2a23\left(x^{2}+y^{2}\right)=2 a^{2}3(x2+y2)=2a2