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avatar+777 

ONLY question c please 

for centre and radius my answer is (3,-2) and r = 5

im not sure what the question means by postive y axis and the method to get to r

 Jan 1, 2019
 #1
avatar+98005 
+1

x^2 - 6x + y^2 + 4y = 12       complete the square on x, y

 

x^2 - 6x + 9    + y^2 + 4y + 4   = 12 + 9 + 4

 

(x - 3)^2  + (y + 2)^2  = 25

 

Since R lies on the positive y axis, it must have the coordinates  (0, a)  where a is positive

 

So......x = 0    and we have

 

(0 - 3)^2 + ( y + 2)^2  = 25

 

9   + ( y + 2)^2  =  25     rearrange as

 

(y + 2)^2 =  16      take the positive root

 

y + 2  =  4

 

y = 2

 

So....R = (0, 2)

 

Here's the graph, YEEEEEET   :  https://www.desmos.com/calculator/j8cvgj36zi

 

 

 

cool cool cool

 Jan 1, 2019
 #2
avatar+777 
+1

thank you very much!

YEEEEEET  Jan 2, 2019

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