Someone please help me see what was done wrong on this problem?

Question

anonymous · Answer

@Mertsj This is my last one for the night, help me out on this last one please!

mertsj · Answer

Don't have time to figure it out tonight.  Sorry

anonymous · Answer

Ok thanks anyway.

anonymous · Answer

i though c(or e as I call it) e^2 = ( a^2 + b^2 )/a^2

anonymous · Answer

@siddarth95 No I'm pretty sure it is c^2=a^2+b^2

anonymous · Answer

@Hero @saifoo.khan @jim_thompson5910 @Edutopia @robtobey @timo86m @AravindG @mathslover

anonymous · Answer

So far I got that c=100 not 200

anonymous · Answer

I think it also has to do with what a is, but i'm not sure how to find a.

anonymous · Answer

@campbell_st @ash2326 @AccessDenied someone please!

anonymous · Answer

@.Sam. @ghass1978

anonymous · Answer

anyone in 11th? at c academy

mertsj · Answer

The first step says that the distance between the foci is 200 so c is 200.  Actually the distance between the foci is 2c so c = 100

mertsj · Answer

So the equation is:
$$\frac{(x-100)^2}{576}-\frac{y^2}{9424}=1$$

anonymous · Answer

Yes, that's what I got... only after spending 30 minutes trying to figure out if "a" was right, only to realize it was :P