Aim: How do we find the locus of points?

The locus of points is the set of all points that satisfy a given condition.

To find the locus of points on a graph you would need to know the condition, for example;

What would the locus of points be 15 meters from Point P? Point P, from the theorem, is the stake to which Fido, the dog, is tied.  His leash is 15 feet long.  The path that Fido can travel at the end of his leash is "the locus of points". The locus of points at a distance of 15 feet from point P is a circle (with center P and radius 15).

In this image, Fido could move freely within the 15 meters of his leash, so any point at the end of his leash would satisfy the condition asked.

There are other conditions such as lines that can include a locus of points.
The locus of points for a single line would be two separate lines on the sides.
 For example what are the locus of points 3 cm from line L, would be the two red lines.

Try this: what are the locus o points from X=2?