Tuesday

September 1, 2015
Posted by **Anonymous** on Sunday, May 13, 2012 at 7:11pm.

possible answers;

(x-5)^2+(y-4)^2=10

(x+5)^2+(y+4)^2=100

(x-2)^2+y^2=25

(x+2)^2+y^2=5

Not sure

- geometry -
**MathMate**, Sunday, May 13, 2012 at 9:32pmStandard equation of a circle with a radius of r and centre (x0,y0) is:

(x-x0)²+(y-y0)²=r²

Centre of circle:

((5-1)/2, (4+(-4))/2)=(2,0)

Out of the four choices, there is only one that has a centre positioned at (2,0).

(hint: refer to the standard equation of the circle)

Radius, r:

Radius of circle = distance from centre to circumference

r = sqrt((5-2)^2+(4-0)^2)=5

This confirms the choice above.

(hint: refer to the standard equation of the circle)

- geometry -
**Anonymous**, Sunday, May 13, 2012 at 9:44pmThis is what I have but not sure if right

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

(x+2)^2+(y-3)^2=25

- geometry -
**MathMate**, Sunday, May 13, 2012 at 10:03pmI do not have the same answer as you.

If AB is the diameter, the centre is located at the mid-point between A and B.

The mid-point between A and B is

((Xa+Xb)/2, (Ya+Yb)/2)=(2,0)

I do not know how you got -2 and 3 for the centre of the circle. Can you explain?

- geometry -
**lilman**, Monday, May 14, 2012 at 11:14amI was looking at wrong problem for this one a I got (x+5)^2+(y+4)^2=100

- geometry -
**MathMate**, Monday, May 14, 2012 at 12:36pmYour answer is not correct.

Please explain how you got

(x+5)^2+(y+4)^2=100 as your answer.

Hint:

Centre of circle is at:

((5-1)/2, (4+(-4))/2)=(2,0)

- geometry -
**lilman**, Monday, May 14, 2012 at 12:51pm(x+2)^2+y^2=5

- geometry -
**MathMate**, Monday, May 14, 2012 at 1:20pm1. Centre is at (2,0)

but

(x+2)^2+y^2=5

has a centre at (-2,0)

2. radius is 5, so the right hand side should be 5^2=25.

- geometry -
**lilman**, Monday, May 14, 2012 at 9:43pmNow I'm definitely lost would you mind explaining the whole process so I might understand?

- geometry -
**MathMate**, Monday, May 14, 2012 at 10:11pmI guess you have not read this on Sunday:

Standard equation of a circle with a radius of r and centre (x0,y0) is:

(x-x0)ē+(y-y0)ē=rē

Centre of circle:

((5-1)/2, (4+(-4))/2)=(2,0)

Out of the four choices, there is only one that has a centre positioned at (2,0).

(hint: refer to the standard equation of the circle)

Radius, r:

Radius of circle = distance from centre to circumference

r = sqrt((5-2)^2+(4-0)^2)=5

This confirms the choice above.

(hint: refer to the standard equation of the circle)

- geometry -
**lilman**, Tuesday, May 15, 2012 at 7:08pmOkay, 9+16=25

so would my answer be (x-2)^2+(y^2)=25

I thiught you had to take the square rt of 25

- geometry -
**MathMate**, Tuesday, May 15, 2012 at 9:34pmYep, you got it, congrats!

I hope you understand how it works.

If not, feel free to post.

- geometry -
**cupcake**, Tuesday, March 5, 2013 at 7:50pmThe answer is (x-2)2+y2=25 i just took it on my quiz and all the other answers are wrong!!! so i got it wrong at first!! but this is the correct one!