The equation 25x2 25y2 = 125 represents which conic section?

25 x² + 25 y² = 125 / : 125 ( we will divide both sides of the equation by 125 )
25 x² / 125 + 25 y² / 125 = 1
x² / 5 + y² / 5 = 1.       At this point someone would think that this is an ellipse
( it is something like: x²/a² + y²/b² = 1 ). But if we multiply both sides of an equation by 5 we will get:
x² + y² = 5. It is a circle with the center at ( 0, 0 ) and a r = √5
This conic section is a circle.