PreCalc
posted by nelly .
True or False:
•Every equation of the form
X^2+y^2+ax+by+c=c
•The radius of the circle
x^2+y^2=9 is 3
•The center of the circle
(X+3)^2+(y2)^2=13 is (3,2)

I do not know what the first one is supposed to be, either a typo or totally false
The second is true
the third has the signs backwards, should be (3 ,2) 
Looks like the first one is intended to be the equation of a circle.
(x^2 + ax) + (y^2 + by) = 0
Unfortunately, if a or b is not zero, there is no real graph.
If a=b=0, then the graph is just the point (0,0).
If there was a typo, giving a "d" on the righthand side, then given suitable a,b,c,d there will be a circle that satisfies the equation. 
Oh yes the first one was a typo it was supposed to be X^2+y^2+ax+by+c=0