Posted by **nelly** on Tuesday, January 10, 2012 at 12:15pm.

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+(y-2)^2=13 is (3,-2)

- Pre-Calc -
**Damon**, Tuesday, January 10, 2012 at 12:30pm
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)

- Pre-Calc -
**Steve**, Tuesday, January 10, 2012 at 12:45pm
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 right-hand side, then given suitable a,b,c,d there will be a circle that satisfies the equation.

- Pre-Calc -
**nelly**, Tuesday, January 10, 2012 at 5:49pm
Oh yes the first one was a typo it was supposed to be X^2+y^2+ax+by+c=0

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