I have an odd question, that I think I have worked out properly, but the answer makes no sense.

What are (a) the x-intercepts,(b) the y-intercepts and(c) the foci of the ellipse

.

I have already determined that the x and y intercepts are:

and

,respectively, meaning that the major axis is vertical as the y-intercept is greater than the x-intercept.

My problem is that when I use the relation:

the result is -9, so c is the square root of -9--which doesn't exist and cant be graphed, meaning I did something wrong.....

What was it that I did wrong?