Write the equation of the circle in standard form, find the center, radius, intercepts and graph the circle. x^2+y^2+4x+2y-20=0

Question

mertsj · Answer

You need to complete the square twice and factor.  Can you do that?

anonymous · Answer

No, this is so new to me! Im stressed out.

mertsj · Answer

Take the x part by itself.  x^2+4x + ?  
What number will complete the square?

anonymous · Answer

6?

anonymous · Answer

Ugh idk

mertsj · Answer

You have to take 1/2 of 4 which is 2.  Square that number.  2 squared is 4

mertsj · Answer

So 4 is the number that completes the square and so now we have:
$$x^2+4x+4$$

mertsj · Answer

The reason that is important is that in can be written in this form:
$$(x+2)^2$$

anonymous · Answer

So then now solve this?

mertsj · Answer

The reason this is important is this:
If you want to find the center and radius of a circle, the equation must  be in this form:

mertsj · Answer

$$(x-3)^2+(y-5)^2=6^2$$

mertsj · Answer

When the equation is in this form, the center is (3,5) and the radius is 6

mertsj · Answer

So that is why we need to get your equation into that form.  Are you with me so far?

anonymous · Answer

I am tagging along

anonymous · Answer

writing it down to follow

mertsj · Answer

So let's write your equation like this:

mertsj · Answer

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