Describe the set of points $z$ in the complex plane that satisfies the following:
a.) $|z-1| + |z+1| = 7$
b.) $|z| = 3|z-1|$
For a, I know that it has the property that their distance from $1$ added to their distance from $-1$ is equal to $7$, but I do not know how to describe it any more further than that.
For b, I know that it must be a circle.