Which condition must be true for the conic section x2a2+y2b2=1\frac{x^2}{a^2} + \frac{y^2}{b^2} = 1a2x2+b2y2=1 to be a circle?
a=ba = ba=b
a>ba > ba>b
a2+b2=1a^2 + b^2 = 1a2+b2=1
a≠ba \neq ba=b