You can
put this solution on YOUR website!Hi,
The general equation of a circle as I'm sure you know is
where (a,b) is the centerpoint and r is the radius. We can make your equation look like this one by completing the square.
Firstly we're looking for the value of a such that
You can either just guess that
or expand and compare coefficients. But
So
Doing the same for y, we get
Finally substituting into the equation we get
So, in the standard form for a circle we get
So we can read off from this that the circle is centered at (-2,-1) with a radius of
Hope that helps,
Kev
You can
put this solution on YOUR website!Equation of a circle is given by
where (a,b) is the center of the circle and r is the radius.
Therefore we need to write x^2 + 4x + y^2 + 2y - 9 = 0 in form above.
Since I have
all i need to do is add 4 and i can re-write it as
However if I am adding 4 then I also need to subtract 4 from the equation
So i get
Similarly for
I can add 1 and re-write as
and similarly subtract 1
Adding 14 on both sides
so center of circle becomes (-2,-1) and radius becomes
You can
put this solution on YOUR website!Find the centre of the circle:
First get your equation into the standard form for a circle. You can do this by "completing the square" in the x-terms and in the y-terms.
Complete the square in the x- and y-terms by adding the square of half the x-, y-coefficients to both sides of the equation.
Factor and Simplify.
Add 9 to both sides.
Now compare this with the standard form for a circle with centre at (h, k).
You can see that the centre of the circle is at (-2, -1)
(
