For Precalc H, I created a series of dynamic Geogebra files, where the teacher or student uses sliders to control the center and the a (and b) values of the conic. The file calculates and graphs the appropriate conic, foci, directrices, etc.

All the files can be downloaded here.

Sample:

Or you can go to geogebratube to run them in your web browser.

Circle

Ellipse (wide) and Ellipse (narrow)

Hyperbola (Left and Right) and Hyperbola (Up and Down)

Parabola (Function) and Parabola (Not a function)

Cheers.