Question

What are the foci of the following graph?

Answer 1

I started with a=1 and b=2 and so c^2=1^2-2^2 it ends up to be c^2=-3 but i don't feel as that's right

Answer 2

Look at the graph, we can see that the foci must be on the x-axis, hence, the coordinate must be under the form of (-x,0) and (x,0). Therefore, we can get rid of A and D

Answer 3

Now, if it is B, the point \((1+\sqrt 3,0)\) has x-coordinate >1, that is it is out of the graph --> cannot be a foci.
Now, we have just.......??

Answer 4

@Loser66 just C left

Answer 5

Yup, but does it make sense to you?

Answer 6

@Loser66 yeah i'll look at this next time i'm having trouble

Answer 7

do you know what is special about the foci

Answer 8

@dan815 Yes, I do. However, in this case, it is easier than the traditional way on finding the foci out by rejecting the wrong one.