what is the radius of a circle with the equation x^2+y^2+6x-2y+3=0 ?

Question

anonymous · Answer

soooo heres what i got

anonymous · Answer

Do you know:
the standard form of a circle
and completing the square?

anonymous · Answer

We'll need both to solve this problem

anonymous · Answer

x^2+6x+....+y^2-2y+....=

x^2+6x+   3^2    +y^2-2y+   (-1)^2  =

which i got (x+3)^2 + (y-1)^2= ???? dont know radius

anonymous · Answer

ohh the beginning equation is this lol  forgot

ikram002p · Answer

ohh ic ,here what you can fix  with ur steps
x^2+6x+ y^2-2y =-3
x^2+6x+....+y^2-2y+....= -3 + .... + ....

anonymous · Answer

$$x^2+y^2+6x-2y+3=0$$

ikram002p · Answer

yep :)
then
x^2+6x+ 3^2 +y^2-2y+ (-1)^2 =-3+ 3^2+ (-1)^2

anonymous · Answer

Ok now take the numbers that you includes on the left side to complete the square to the other side, because what you do to one sides you have to do to the other

anonymous · Answer

so add 3^2 and (-1)^2 to the right side of the equation

mathmale · Answer

doulikepiecauseidont 's question is very pertinent, and I'dd suggest that you, @meln_n, review both concepts:

Do you know:
the standard form of a circle
and completing the square?

anonymous · Answer

And bring the constant of 3 to the other side so you would subtract it from the number you just added to the right side

anonymous · Answer

sooo finally product 

$$(x+3)^2+(y-1)^2=7^2$$

ikram002p · Answer

^_^ nice work @meln_n

anonymous · Answer

yay soo would radiu be 7 or 49 ???

mathmale · Answer

What do you think?  Look carefully at the std. eq'n. of a circle.

anonymous · Answer

i believe 7 because in the equation theres a r^2

ikram002p · Answer

remember this formula for circle equation
$\large (x-x_0)^2+(y-y_0)^2=r^2$

such that $ (x_0,y_0) $ is the center and r is the radius

jdoe0001 · Answer

hmm

anonymous · Answer

yes n_n remember

ikram002p · Answer

@jdoe0001  why hmming :P
so @meln_n  whats ur answer ?

jdoe0001 · Answer

heheh

anonymous · Answer

7 n_n ...

ikram002p · Answer

why hehehing nw :P

anonymous · Answer

correct so in the std. eq
n, the would be square so the radius squared gives you 7 so what is the radius?

jdoe0001 · Answer

x^2+6x+ 3^2 +y^2-2y+ (-1)^2 =-3+ 3^2+ (-1)^2
                                                                        ^

-3+9+1 = 7 $\ne 7^2$

anonymous · Answer

yay ! thank you everyone Conic section is getting to me -_- lol

anonymous · Answer

Here's a graph of the circle just to confirm your answer of the radius http://www.wolframalpha.com/input/?i=x%5E2%2By%5E2%2B6x-2y%2B3%3D0

ikram002p · Answer

XD haha lol yeah sry meln

ikram002p · Answer

@meln_n check what @jdoe0001 said xD

jdoe0001 · Answer

doulikepiecauseidont    I think that deserves a nice apple pie :P

anonymous · Answer

Well, not for me