## mskyeg one year ago What are the foci of the ellipse? Graph the ellipse. 18x^2 + 36y^2 = 648

1. mskyeg

2. Mertsj

Get the equation into the right form by dividing both sides by 648

3. mskyeg

I did that im stuck at x^2/36 + y^2/18 = 1

4. Mertsj

Is the big number under the x or under the y?

5. mskyeg

x

6. Mertsj

That tells you that the major axis is horizontal so the vertices and foci are on the x axis and that a^2 = 36. Are you with me?

7. mskyeg

ya

8. mskyeg

b^2=18

9. Mertsj

Yep. So find c

10. mskyeg

how?

11. mskyeg

like wats the equation

12. Mertsj

do you mean "what is the question"?

13. mskyeg

i said equation

14. mskyeg

to find c

15. Mertsj

Do you mean what equation relates a, b, and c?

16. mskyeg

i guess ya

17. Mertsj

a^2-b^2=c^2

18. mskyeg

c=+/- 9?

19. mskyeg

not an option

20. Mertsj

|dw:1363368768837:dw|

21. Mertsj

What is c?

22. Mertsj

Can you find C or are we done???

23. mskyeg

found it thanx

24. Mertsj

What is it?

25. mskyeg

3 next to the square root of 2. dont knw how to write that in the chat box

26. Mertsj

3sqrt2 and -3sqrt2

27. mskyeg

ya

28. Mertsj

So the focal points are (3sqrt2,0) and (-3sqrt2,0)

29. mskyeg

ya