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ive been trying to solve this for a while but keep getting it wrong 

cerenetie  Feb 22, 2018
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x^2 + y^2 - 4x + 2y - 11  = 0

 

Rearrange as

 

x^2- 4x + y^2 + 2y  =  11

 

We need to complete the square on x  an y 

 

I'm assuming that you know how to do this...if, not...here's a good resource :

 

http://www.purplemath.com/modules/sqrcircle.htm

 

x^2 - 4x + 4 + y^2 + 2y + 1  =  11  + 4  + 1       factor and simplify

 

(x - 2)^2  +  (y + 1)^2   =  16

 

In the form    ( x - h)^2  + (y - k)^2  = r^2

 

The center  is  (h, k)   and the radius  = r  ......so....we can write

 

( x - 2)^2  +  ( y  - (-1) )^2  =   4^2

 

The center is   (2, - 1)   and the radius  is  4

 

 

cool cool cool

CPhill  Feb 22, 2018

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