Okay, how do I convert from standard form of a circle to general form?

Specifically, the equation I'm currently trying to convert is (x + 4)^2 + (y - 2)^2 = 4

Question

Okay, how do I convert from standard form of a circle to general form?

Specifically, the equation I'm currently trying to convert is (x + 4)^2 + (y - 2)^2 = 4

anonymous · Answer

what is a general form?

anonymous · Answer

x^2 + y^2 + ax + by + c = 0

anonymous · Answer

^ general form

zepdrix · Answer

Hmm so I guess you just have to expand out the brackets.
Do you remember how to multiply a pair of binomials?$$\Large\bf\sf (x+4)^2\quad=\quad (x+4)(x+4)\quad=\quad ?$$

anonymous · Answer

Hmm, yes, hold on let me try this, I think I might know it.

(x + 4)^2 = x^2 + 8x + 16
(y - 2)^2 = y^2 - 4y + 4

So x^2 + y^2 + 8x - 4y + 20 = 4
x^2 + y^2 + 8x - 4y + 16 = 0

anonymous · Answer

Is that right? Did I do it right?

zepdrix · Answer

Hmm why did your +4 from the y brackets get moved to the right side? :o

anonymous · Answer

wait what

anonymous · Answer

It wasn't, but in the standard form, the equation was equal to 4, so I had to move that over to the left side to get 0

zepdrix · Answer

Ohhhh it started equal to 4 haha :) good good good.
Ok yes good job!

anonymous · Answer

Yaaay! lol First time I've ever figured something like that out xD thank you!

anonymous · Answer

you're welcome :)