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The standard form of the equation of a circle is (x−4)2+(y−2)2=9.

 

What is the general form of the equation?

x2+y2+8x+4y+11=0

x2+y2−8x−4y−29=0

x2+y2+8x+4y−29=0

x2+y2−8x−4y+11=0

jbouyer  May 15, 2017

Best Answer 

 #1
avatar+7339 
+3

(x - 4)2 + (y - 2)2 = 9

 

We want to multiply this out.

(x - 4)(x - 4)   + (y - 2)(y - 2) = 9

(x2 - 8x + 16) + (y2 - 4y + 4) = 9

x2 - 8x + 16 + y2 - 4y + 4 = 9

 

Rearrange and subtract 9 from both sides.

x2 + y2 - 8x - 4y + 16 + 4 - 9 = 0

x2 + y2 - 8x - 4y + 11 = 0

hectictar  May 15, 2017
 #1
avatar+7339 
+3
Best Answer

(x - 4)2 + (y - 2)2 = 9

 

We want to multiply this out.

(x - 4)(x - 4)   + (y - 2)(y - 2) = 9

(x2 - 8x + 16) + (y2 - 4y + 4) = 9

x2 - 8x + 16 + y2 - 4y + 4 = 9

 

Rearrange and subtract 9 from both sides.

x2 + y2 - 8x - 4y + 16 + 4 - 9 = 0

x2 + y2 - 8x - 4y + 11 = 0

hectictar  May 15, 2017

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