Question

What are the foci of the Ellipse? 36x^2+9y^2=324

Answer 1

You can figure this out by writing the equation in ellipse form.

Answer 2

So you have to divide both sides by 324.

Answer 3

why 324? Because 324 divides evenly by both 9 and 36

Answer 4

afterwards your equation should look like this

\[x^2/9 + y^2/36 =1\]

Answer 5

\[c^2=a^2-b^2\]

Answer 6

But what are a and b?

Answer 7

a^2 is the number under y^2. b^2 is the number under x^2

Answer 8

So c=sqrt(36-9)

Answer 9

c=5. Because c=5, the foci are located at (0,5) and (0,-5)

Answer 10

http://www.mathwarehouse.com/ellipse/images/focus_equation_better.gif
heres a picture if you still need help

Answer 11

Okay Thankyou so much helped a lot!