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avatar+212 

What is the equation of the circle in general form?

 A. x2+y2−4x−2y−2=0

 

B. x2+y2+4x+2y−44=0

 

C. x2+y2−4x−2y−44=0

 

D. x2+y2+4x+2y−2=0

lysxsa  May 23, 2018
 #1
avatar+92855 
+2

The center is ( -2, -1) and the radius is 7

 

So....using   (x - h)^2  + ( y - k)^2  = r^2  where   (h , k) is the center and r is  the radius, we have

 

( x - -2)^2  + ( y - - 1)^2  = 7^2

 

(x + 2) ^2  + (y + 1)^2  = 49         expand   and simplify

 

x^2  + 4x + 4  + y^2   + 2y  + 1  = 49

 

x^2 + y^2 +  4x   + 2y  +  5 = 49       subtract 49 from  both sides

 

x^2 + y^2  + 4x  + 2y  - 44  =  0      ⇒   Answer  "B"

 

 

 

cool cool cool

CPhill  May 23, 2018
 #2
avatar+212 
+1

THank you!

lysxsa  May 23, 2018

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