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Find an equation (with integral coefficients and constants) for the set of points that are equidistant from A(8, -3, 2) and B(4,5,-4). Name two points (with integral coordinates) that satisfy this equation.

2007-03-11 17:00:34 · 4 answers · asked by clock 2 in Science & Mathematics Mathematics

i got the first part so far. for the first part i did this:
(x-8)^2+(y+3)^2+(z-2)^2=(x-4)^2+(y-5)^2+(z=4)^2
so the equation for the set of pts that are equidistant from A and B is 8x-16y+12z=20 which simplifies to 2x-4y+3z=5, but i've been staring at this for the past hour and i still can't figure out how to get the 2 points that satisfy this equation and are INTEGRAL numbers

2007-03-11 17:03:15 · update #1

4 answers

EDIT: Check your algebra: should be - 12z instead of +12z, which leads to 2x-4y-3z=5. Building on your work, though, one integer solution is the midpoint of the two points: (6,1,-1). Another is (1,0,-1)

rhsaunde... is incorrect. The set of points equidistant from two points in 3-space is a plane, perpendicularly bisecting the segment between the two points.

2007-03-11 17:12:01 · answer #1 · answered by mitch w 2 · 0 0

The locus of poiints in 3space that are equidistant to two given points is a plane thru the midpoint between the two given points and perpendicular to the line segment between the two given points.

The two given points are:
A(8,-3,2) and B(4,5,-4)

First find the midpoint M.

M = (A + B)/2 = [(8+4)/2,(-3+5)/2,(2-4)/2] = (6,1,-1)

M is contained in the plane. Now find the plane's normal vector. It is the same as the directional vector of the line between A and B.

v = A - B = <8-4,-3-5,2+4> = <4,-8,6>
We can select a mulitple of this. Lets divide by and select:
v = <2,-4,3>

The equation of the plane is

2(x - 6) - 4(y - 1) + 3(z + 1) = 0
2x - 12 - 4y + 4 + 3z + 3 = 0
2x - 4y + 3z - 5 = 0

Find two integral points on the plane.

One point is M(6,1,-1)

Set y = 0. Then we have:

2x + 3z - 5 = 0
x = z = 1
So another point is P(1,0,1).

Two points with integer coefficients are:
M(6,1,-1) and P(1,0,1).

2007-03-11 21:08:50 · answer #2 · answered by Northstar 7 · 0 0

We will first want the distance between the points, which is sqrt(4^2 + 8^2 + 6^2), or sqrt(116), roughly 11.5. Then we can structure a set of ellipses, using (x-8)*2 + (y+3)*2 + (z-2)^2 + (x-4)^2 + (y-5)^2 + (z+4)*2 = k^2, where k is any integer greater than or equal to 12. You can grind through the algebra to find two other points.

2007-03-11 17:11:02 · answer #3 · answered by Anonymous · 0 0

this is going to be a plane that is perpendicular to the line joining the 2 points and passing through the middle point of their segment

2007-03-11 17:17:58 · answer #4 · answered by Anonymous · 0 0

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