Question

What is the value of a for the following circle in general form? x^2+y^2+ax+by+c=0

Answer 1

Just a, b, and c, and no specific values?

Answer 2

I see, well, the easiest way to solve this is to determine the centre and the radius of your circle.
Once you do that, you'll be able to arrive at the general equation of the circle with ease.

So... what is the centre of this circle?

Answer 3

What are the steps to find the center?

Answer 4

Uhh, well, there are no steps, it seems you have to be able to determine it from your graph... look at it, what point is the centre of your circle?

Answer 5

3,-1?

Answer 6

that is correct :)
And the radius?

Answer 7

How do you find radius?

Answer 8

Again, it would seem you have to rely on the graph... from the centre, navigate to a point on the edge of the circle and somehow, measure its distance.
I recommend going horizontally or vertically, much more precise that way :)

Answer 9

Or, let's be specific :)
The point (7,-1) is on the circle, so the distance from that point from the centre (3,-1) must be the radius :)

Answer 10

OHHHHH.Okay I understand!!!

Answer 11

So the radius is...?

Answer 12

So it would just simply be 4?

Answer 13

That is correct :)
So once you know the centre \(\large (\color{red}h \ , \color{green}k)\) of your circle as well as its radius \(\large \color{blue}r\), then the equation of the circle in standard form would just be \[\Large (x-\color{red}h)^2 + (y-\color{green}k)^2=\color{blue}r^2\]

Answer 14

Ah okay!I think I can do the rest from here, let me try hm.Thank you!(:

Answer 15

No problem, and good job :)