## anonymous one year ago Algebra question?

1. anonymous

Decide whether or not the equation has a circle as its graph. If it does, give the center a$x^2+y^2-6x+2y=-9$nd the radius. If it does not, describe the graph.

2. anonymous

I know I need to rewrite into center radius form but i only get this far: $(x^2-6x)+(y^2+2y)=-9$

3. nincompoop

what is the general form for circle?

4. anonymous

$(x-h)^2+(y-k)^2=r^2$ ?

5. nincompoop

does yours look like that?

6. anonymous

no:(

7. nincompoop

http://www.mathsisfun.com/algebra/circle-equations.html there you have it

8. anonymous

$(x-6)^2+(y-2)^2=-9^2$

9. nincompoop

can you expand the left hand side?

10. anonymous

wait, it'd be x+6 right? not x-6

11. nincompoop

you complete the squares

12. anonymous

$(x+6)^2+(y-2)^2=-9^2$

13. nincompoop

look at the link I shared it shows you step by step using similar problem

14. anonymous

ok hang on

15. anonymous

I am closing to finding the answer will you tell me if its right?

16. anonymous

Ok, I got (3,-1) and now cant figure out to how find the radius?

17. anonymous

@nincompoop

18. dehelloo

hmm https://www.youtube.com/watch?v=qh5hNY83UA4 is an accurate video that follows up the process

19. anonymous

am I completely wrong? :/ I have trouble with longer problems. can anyone solve this exact problem so I can see where I went wrong?

20. anonymous

Can anyone just give me answer at least? Trying to finish my homework up and this is my last problem left.

21. anonymous

@nincompoop @dehelloo

22. anonymous

AFK.

23. Nnesha

he died ?? ;-; nin!!

24. anonymous

Haha I don't know what happened!

25. Nnesha

$$\color{blue}{\text{Originally Posted by}}$$ @rawrolivia $(x+6)^2+(y-2)^2=-9^2$ $$\color{blue}{\text{End of Quote}}$$ you didn't complete the square

26. anonymous

I'll show you what I did. Give me a moment to type it all

27. Nnesha

okay

28. anonymous

$x^2+y^2-6x+2y=-9 --> (x^2-6x+9)+(y^2+2y+1)=-9+9+1$ $(x-3)^2+(y+1)^2=1$ (3,-1)

29. anonymous

...I think I got the answer but I'm unsure. Sorry I've been meaning to reply for awhile but uh.. I probably got it wrong but this is what I got from it: Center of the circle is: C = (-6, 2) Radius of the circle is 9.

30. anonymous

...I think I got the answer but I'm unsure. Sorry I've been meaning to reply for awhile but uh.. I probably got it wrong but this is what I got from it: Center of the circle is: C = (-6, 2) Radius of the circle is 9.

31. Nnesha

yes your work is correct remember to complete the square we should we should divide b by 2 and then add (b/2)^2 to the opposite side that's how u got +9 and 1 at right side -9+9+1= 1 so yes your work is correct good job!

32. anonymous

ok but @peridot got a different answer :/

33. Nnesha

$x^2+y^2-6x+2y=-9 --> (x^2-6x+\color{Red}{9})+(y^2+2y+1)=-9+9+1$ how did you get 9 ? explain

34. anonymous

-6 = -3, -3^2 =9

35. Nnesha

-6=-3 ? is there a typo ?

36. anonymous

I thought you had to take half of the middle number, and then square it

37. Nnesha

oh yes so -6/2 = -3 -6 isn't equal to -3 alright and yes (-3)^2 =9 and like i said you should (b/2)^2 to the right side $x^2+y^2-6x+2y=-9 --> (x^2-6x+\color{Red}{9})+(y^2+2y+1)=-9+\color{ReD}{9}+1$

38. Nnesha

and same thing with one you take half of the middle term 2/2 =1 and then take square add to the right side $x^2+y^2-6x+2y=-9 --> (x^2-6x+\color{Red}{9})+(y^2+2y+1)=-9+\color{ReD}{9}+\color{blue}{1}$ -9+9 +1 = 1 so if your work is correct then obviously your answer is correct

39. anonymous

ok but I need to find out what the radius is now

40. Nnesha

$$\color{blue}{\text{Originally Posted by}}$$ @rawrolivia $(x-h)^2+(y-k)^2=r^2$ ? $$\color{blue}{\text{End of Quote}}$$ general form of the circle write where r is the radius

41. Nnesha

now compare your equation with that general form what is the radius in that equation ?

42. anonymous

43. anonymous

going to walmart, can i just please have answer? this is confusing me more than it should :(

44. Nnesha

$$\color{blue}{\text{Originally Posted by}}$$ @rawrolivia So radius is 1? $$\color{blue}{\text{End of Quote}}$$ yes right

45. Nnesha

46. Nnesha

$(x-h)^2+(y-k)^2=r^2$ general form of the circle write where r is the radius and (h,k) is the center

47. nincompoop

I went to school to attend a session. Sorry. Let me know if you want to further learn or go over about circles.