The equation of

have the four common points , (0,-3),(0,3),(-3,0),(3,0).

These points are intersections with x-axis or y-axis.

So substance x=0 or y=0 for this equation.

Substance x=0

Substance y=0

Therefore ,when n is any number ,the equation have the four common points

of (0,-3),(0,3),(-3,0),(3,0).