 My Math Forum show that the equation x^2+y^2+4x+4=0 is a circle and determine its centre and radius

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 September 1st, 2017, 10:49 AM #1 Newbie   Joined: Aug 2017 From: Luweero, Uganda Posts: 4 Thanks: 0 Math Focus: differentiation show that the equation x^2+y^2+4x+4=0 is a circle and determine its centre and radius How can I Show that the equation x^2+y^2+4x+4=0 is a circle and determine its centre and radius? Last edited by skipjack; September 1st, 2017 at 11:05 AM. September 1st, 2017, 10:53 AM #2 Math Team   Joined: Dec 2013 From: Colombia Posts: 7,697 Thanks: 2681 Math Focus: Mainly analysis and algebra Perform a substitutions for $x$ and $y$ that result in the form $u^2 + v^2 = r^$. Are you sure your equation is correct? It looks like an odd sort of circle to me. September 1st, 2017, 11:06 AM #3 Global Moderator   Joined: Dec 2006 Posts: 21,110 Thanks: 2326 It's a single point. I've moved this problem to Geometry. September 1st, 2017, 11:09 AM #4 Banned Camp   Joined: Mar 2015 From: New Jersey Posts: 1,720 Thanks: 126 Irrelevant after moved. Delete button in Edit doesn't seem to work Last edited by zylo; September 1st, 2017 at 11:11 AM. September 2nd, 2017, 05:30 AM #5 Math Team   Joined: Jan 2015 From: Alabama Posts: 3,264 Thanks: 902 Complete the square in x: $\displaystyle x^2+ 4x= x^2+ 4x+ 4- 4= (x- 2)^2- 4$ (The graph of $\displaystyle x^2+ y^2+ 4x+ 4= 0$ is NOT a circle. It is the single point (-2, 0).) Tags centre, circle, determine, equation, radius, show Thread Tools Show Printable Version Email this Page Display Modes Linear Mode Switch to Hybrid Mode Switch to Threaded Mode Similar Threads Thread Thread Starter Forum Replies Last Post pjlloyd100 Calculus 3 November 11th, 2013 01:21 PM andreaugust Algebra 2 October 28th, 2013 10:29 AM berkeleybross Algebra 4 December 8th, 2010 08:15 PM aschenbr.rach Calculus 1 March 7th, 2010 12:52 PM squeeze101 Algebra 3 November 21st, 2008 07:37 PM

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