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The graph of the equation 4x^2 + 20x + 4y^2 - 24y + 21 = 0 is a circle. Find the radius of the circle.

 

thank you

 Mar 13, 2020
 #1
avatar+21827 
+1

4x^2 + 20x + 4y^2 - 24y + 21

Divide thrugh by 4

 

x^2 +5x +y^2-6y = -21/4      ' complete the square '   for x and y

 

(x+2.5)^2    +   (y-3)^2  = -21/4  + 6.25  + 9 

                                      =  -21/4  + 25/4 + 36/4 = 40/4 = 10

 

10 = r^2     r = sqrt 10

 Mar 13, 2020
 #2
avatar+11681 
+1

The graph of the equation 4x^2 + 20x + 4y^2 - 24y + 21 = 0 is a circle. Find the radius of the circle.

laugh

 Mar 13, 2020
edited by Omi67  Mar 13, 2020
edited by Omi67  Mar 13, 2020

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