Question

A circle is shown on the coordinate plane below.

Circle that contains points 3, 0; 1, 2; negative 1, 0; 1, negative 2.

What is the equation of this circle?

(x – 1)2 + y2 = 2

(x + 1)2 + y2 = 4

(x + 1)2 + y2 = 2

(x – 1)2 + y2 = 4

Answer 1

Please help, will give a medal to best answer

Answer 2

Hint:

Let A be the point (-1,0) and B be the point (3,0)

Now find the midpoint of AB. This will give you your center.

Answer 3

I have no idea how to find a midpoint, I'm not looking for an anwer as much as I'm looking for an explaination.

Answer 4

example

midpoint of (6,7) and (8,9)

add up the x coordinates and divide by 2

x = (6+8)/2 = 14/2 = 7

add up the y coordinates and divide by 2

y = (7+9)/2 = 16/2 = 8


So the midpoint in this example is (7,8)

Answer 5

you can try to plug inthe point values into the given equations to see which one fits the best.

Answer 6

otherwise, it hard to parse the information that you have preseneted without going into alot of manual labor :)

Answer 7

okay so we found the midpoint, what now?

Answer 8

what did you get for the midpoint

Answer 9

I didn't do it, can you just show me in depth?

Answer 10

-2 /2
= -1?

Answer 11

A is the point (-1,0) and B is the point (3,0)

midpoint

x = (-1+3)/2

x = 2/2

x = 1

y = (0+0)/2

y = 0/2

y = 0

midpoint of AB is (1,0)

Answer 12

okay, so our midpoint is 1,0; now what?

Answer 13

that's the center of the circle

Answer 14

the distance from the center (1,0) to either A or B is what?

Answer 15

so aslong as you find the midpoint, you find the center of the circle.

Answer 16

where is A, and B

Answer 17

A(-1,0) and B(3,0)

Answer 18

the distance would be 2

Answer 19

right?

Answer 20

so the radius is 2

Answer 21

okay, so now we know our radius. Now what?

Answer 22

(x – h)^2 + (y-k)^2 = r^2

(x – 1)^2 + (y-0)^2 = 2^2

(x – 1)^2 + y^2 = 4

Answer 23

(h,k) is the center, r is the radius

Answer 24

jim_thompson5910, you are very very smart I appreciate all your help. Thank you sooooooooooo much, math is the worst subject I participate it. Not grade wise, I have an A. But just doing the questions nearly bore me to death and I just can't understand them without needing someone to help me constantly. Again; thank you. How do I give out a medal?

Answer 25

just click best response, you're welcome

Answer 26

maybe try making the questions more exciting so they don't seem so boring?

Answer 27

I guess, but it's just the numbers itself that bore me out; no matter what kind of information I input into the equation... :(

Answer 28

i gotcha, well maybe make a game out of it or something? hmm not sure

Answer 29

There's two more questions I need help with, can you please go over them with me?

Answer 30

and I guess that makes sense?

Answer 31

it's just a random thought lol, but sure what's the question

Answer 32

Ryan’s teacher asked him to graph circle E with equation (x – 5)2 + y2 = 25. Below is the graph he submitted.

Circle E that contains points 30, 0; 5, negative 25; negative 20, 0; 5, 25.

What, if anything, did Ryan do wrong when graphing this equation?

He graphed a circle with a radius of 25 instead of a radius of 5.

He graphed a circle with center at (5, 0) instead of at (-5, 0).

He graphed a circle with center at (5, 0) instead of at (25, 0).

Ryan’s graph is accurate.

Answer 33

his radius is too big, if you graph the circle, you'll get a radius of 25 not 5

Answer 34

his radius should be 5

Answer 35

thank you so much, ok next one?

Answer 36

how would you graph it exactly?

Answer 37

either plot the center (5,0) and draw a circle with a radius of 5 around it

or

draw a circle through those given points (which is harder to do)

Answer 38

so plot the center the use a compass with the sizing and draw a circle?

Answer 39

exactly

Answer 40

I see! Okay, next one and last one?

Answer 41

go for it

Answer 42

Circle T has an equation of x2 + (y + 10)2 = 25. Which graph represents circle T?

Answer 43

not sure if I can post the actual graphs themselves

Answer 44

any idea @jim_thompson5910

Answer 45

you can take screenshots and post them

Answer 46

tell me if you can open this link

http://learn.flvs.net/webdav/assessment_images/educator_geometry_v14/pool_Geom_3641_0802_05/image0034e849a3b.gif

Answer 47

it's giving me a cookie error...whatever that is

Answer 48

how do I take a screen shot on a macbook pro?

Answer 49

hmm one sec

Answer 50

have a look at this tutorial

http://graphicssoft.about.com/od/screencapturemac/ht/macscreenshot.htm