In the case of a=1 , b=1 , and k=1, the graph of the equation is as following;
Let's try to change a for various number, with the b and k (b=1,k=1) are fixed!
a=2
a=3
a=4
If the number of a is bigger number, the graph is expand and the shape is similar to circle having radius of a graduary.
Let's try to change b for various number,with a andk are fixed (a=1,k=1)!
b=2
b=3
b=4
As changing the number of b begger, expanding inside ring.
Let's try to change the number of k for various number,with a=1 , b=1 !
k=2
k=3
k=4
k=5
It seems that the number of k and the the number of k are same number.