We use cookies to personalise content and advertisements and to analyse access to our website. Furthermore, our partners for online advertising receive pseudonymised information about your use of our website. cookie policy and privacy policy.
 
+0  
 
+1
287
1
avatar

The center of the circle with equation $x^2+y^2=8x-6y-20$ is the point $(x,y)$. What is $x+y$?

 Jan 15, 2018
 #1
avatar+101234 
+1

\($x^2+y^2=8x-6y-20$\)

 

Write as

 

x^2  -  8x  +  y^2   +  6y   =  -20            

 

Complete the square on x and y

 

x^2  - 8x  + 16  +  y^2  + 6y  +  9   =  -20  + 16 + 9

 

(x - 4)^2   +  (y  + 3)^2  =  5

 

The center is   (4, -3)  =  (x, y)

 

So   

 

x + y  =   4  -  3     =   1

 

 

cool cool cool

 Jan 15, 2018

11 Online Users

avatar
avatar
avatar