Hey Gang:

I have my final exam tomorrow night and I have "preparation test" I was given, so I have been finding like example questions to quiz myself - here are my weakspots that I can quite get, as there are no samples in all of my textbooks that the same "type":

1. State the sum of focal radii for the ellipse with the equation:

I get 2 different answers via this:

, therefore, a=4

, therefore, b=3

, therefore c=5, therefore the foci=5, therefore sum of focal radii=10

OR, according to my book, sum of focal radii=2a, therfore 2(4)=8?

2. State the equation of the directrix for the parabola with the vertex (0,0) and focus (0, -3).

3. Solve for x:

I have NO idea how to approach this one. I have never seen a variable *in* an exponent. A hint or two, please on how to start? (I am probably just mental-blocking, so a push in the right direction will most likely make me go "AHH!")

Thanks for all & any help!