Question

Write the standard equation of the circle below.





Answer

(x + 1)2 + (y - 2)2 = 1

(x - 1)2 + (y - 2)2 = 1

(x + 1)2 + (y + 2)2 = 1

(x - 1)2 + (y - 2)2 = 1

Answer 1

Do you have an image of the circle to post?

Answer 2

sorry its bad its at -1,2

Answer 3

I'm sorry, but that is kind of a bad drawing...is the center at (-1, 2)? Not that my drawing is any better... ; )

Answer 4

yea
it is

Answer 5

The standard equation for a circle is\[(x-h)^{2}+(y-k)^{2}=r ^{2}\]Are you familiar with that?

Answer 6

somewhat

Answer 7

The h and the k indicate that the center is something other than the origin which is (0, 0).

Answer 8

ok

Answer 9

Your center is at (-1, 2), so you know right away some of what you need to begin filling in the equation, which is to fill in -1 for h and 2 for k). But keep in mind, the signs are opposite from what your coordinate reflects. Like this:

Answer 10

\[(x+1)^{2}+(y-2)^{2}=r ^{2}\]

Answer 11

ok

Answer 12

yea i get that part now

Answer 13

This is because the standard form must be written in (x - h) and (y - k). So if your center x coordinate is -1, it fits into the formula like this (x - (-1)) which equals (x + 1). Likewise for the y coordinate. It fits into the formula like this: (y - (+2)) which equals (y - 2). See that?

Answer 14

Now we just need to determine the radius. Let me get a better look at your circle you drew...

Answer 15

but its bad

Answer 16

Do we have a point on the circle? I have to know a point on the circle in order to determine the radius.

Answer 17

and yea i understand the (x+1) + (y-1)=r

Answer 18

it doesn't say

Answer 19

Don't forget those are squared terms. And if it doesn't say on your work, I need you to tell me something that only you can determine from the picture. Do you actually have a drawing or an image that you took the circle from?

Answer 20

um i doont have one

Answer 21

Then what do you have? A picture? A list of specifics about the circle? Anything other than the center?

Answer 22

Here is what I am talking about. Let me post my own pic as an example:

Answer 23

ok

Answer 24

oh its not asking for radius

Answer 25

You don't need to complete the circle's equation, then?

Answer 26

no


(x + 1)2 + (y - 2)2 = 1

(x - 1)2 + (y - 2)2 = 1

(x + 1)2 + (y + 2)2 = 1

(x - 1)2 + (y - 2)2 = 1

Answer 27

I get it! Which one is it from that list, then? We determined the center, and obviously they gave you the radius, which is 1, so which of those is the correct one?

Answer 28

the x=1 y-2 ?

Answer 29

so a?

Answer 30

It's the first choice in your list. Just remember how to find the center AND then how to write it into the equation and you'll be fine!

Answer 31

Good job!

Answer 32

And thank you for the medal!

Answer 33

thx i medaled and fanned u u wl be hearing from me again because ur smart

Answer 34

Actually, I teach this every day...I'm not that smart...just experienced! And thank you!

Answer 35

well ur good at it