As you see, there are two types of graph. On the one hand, red and blue are closed lines. On the other hand, green and purple, are not closed at least in this frame, which may not be closed any where.

Each of two types of graphs has own common character in their exponents for x and y. That is about to be an even or odd number. In the case that the formula has an even exponent for x and y like the red and blue curves, they are close curves such as a circle. The red line is completely a circle, and the blue line is the shape between a circle and a square.

In the case that the formula has an odd exponent for x and y like green and purple curves, they are not close cuves.

The graph of the formulais to be a close line graph that is nearly a square because the exponent of the formula has an even number 24.

The graph of is below.

The graph of the formula is not a close line graph because the exponent of the formula has an even number 24.

The graph of is below.