Question 876661
help me find the standard equation of the circle passing thru the point (-3,1) and containing the points of intersection of the circles x^2 + y^2 + 5x = 1 & x^2 + y^2 + y = 7. The soln: (x+5/9)^2 + (y+7/18)^2 = 569/100. thank you!
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That is not the correct solution:

That's because {{{(x+5/9)^2 + (y+7/18)^2 = 569/100}}} 

does not pass through (-3,1)

Substitute x=-3, y=1 in 

{{{(x+5/9)^2 + (y+7/18)^2 = 569/100}}}

{{{(-3+5/9)^2 + (1+7/18)^2 = 569/100}}}

{{{(-27/9+5/9)^2 + (18/18+7/18)^2 = 569/100}}}

{{{(-22/9)^2 + (25/18)^2 = 569/100}}}

{{{484/81 + 625/324 = 569/100}}}

{{{1936/324+625/324)= 569/100}}}

{{{2561/324 = 589/100}}}

Since the answer given above doesn't pass through (-3,1),
there has to be a typo somewhere.  Check the problem
again very carefully for a sign error or some other small
error.  Type it very carefully in the thank-you note, and I'll 
get back to you.

Edwin</pre>