Help with Circle Geometry Homework - Calculate Co-ordinates of M

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To calculate the coordinates of point M, which is the center of a circle containing points A(2,3) and B(-1,6), three equations are needed due to three unknowns: c, d, and the radius r. The standard form of the circle's equation is crucial, and substituting the coordinates of points A and B into this equation will yield two equations. Additionally, substituting the coordinates of M into the line equation 2x + 5y + 1=0 provides a third equation. After working through these equations, the coordinates of M are determined to be (-3,1).
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Homework Statement



In the diagram alongside, A(2,3) and B(-1,6) lie on the circle with centre M(c,d).
M is also a point on the straight line defined by 2x + 5y + 1=0. The diagram is on the attached doc file.

Calculate the co-ordinates of M.

Homework Equations



analytical methods only!

The Attempt at a Solution


Im really stuck:frown:
 

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You have 3 unknowns (c, d, and the radius r of the circle), so you need 3 equations to find them. Try to answer the following questions. They should help you.

1.) What is the standard form of the equation form of a circle with center (c,d) and radius r?
2.) What do you get when you plug the point (x,y)=(-1,6) into that equation?
3.) What do you get when you plug the point (x,y)=(2,3) into that same equation?
4.) What do you get when you plug the point (x,y)=(c,d) into the equation of the given line?

That should get you started.
 
Tom Mattson said:
You have 3 unknowns (c, d, and the radius r of the circle), so you need 3 equations to find them. Try to answer the following questions. They should help you.

1.) What is the standard form of the equation form of a circle with center (c,d) and radius r?
2.) What do you get when you plug the point (x,y)=(-1,6) into that equation?
3.) What do you get when you plug the point (x,y)=(2,3) into that same equation?
4.) What do you get when you plug the point (x,y)=(c,d) into the equation of the given line?

That should get you started.

Thank you I got it. M is (-3,1):biggrin:
 
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