"Find point C on the X-axis so that AC+BC is a minimum"

These are just thrown into an assignment on Reflections, and I for one don't get it.

We've got about 20 problems of them, so I can't really just try and hope it's right, either.

Examples:

A(1,4) B(4,2)

A(-2,3) B(6,3)

A(-3,2) B(-6,4)

A(1,-3) B(-3,-3)

I'm not even sure what it's asking for... Am I supposed to find a new point that would create the shortest possible line segments if graphed, or what?

If it's something else, what formulae would I use?