SOLUTION: Please solve the following for me. Find the equation of the plane through the three points (1,-1,-1),(-3,2,-1) and (-2,3,0)

Algebra ->  Linear-equations -> SOLUTION: Please solve the following for me. Find the equation of the plane through the three points (1,-1,-1),(-3,2,-1) and (-2,3,0)      Log On


   



Question 984079: Please solve the following for me.
Find the equation of the plane through the three points (1,-1,-1),(-3,2,-1) and (-2,3,0)

Answer by Edwin McCravy(20055) About Me  (Show Source):
You can put this solution on YOUR website!

Find two non-parallel vectors both parallel to or "in" the plane and 
take their cross product to find a normal vector n to the plane.


matrix%281%2C7%2C%22%3C%22%2Ca%2C%22%2C%22%2Cb%2C%22%2C%22%2Cc%2C%22%3E%22%29

Then the equation of the plane will be this dot product set equal to 0
so that the normal be perpendictular to the plane.

 n

or

a%28x-x%5B1%5D%29%2Bb%28y-y%5B1%5D%29%2Bc%28z-z%5B1%5D%29=0 

which is known as the "point-normal" form of the equation of a plane:

---------------------------------

To find two nonparallel vectors both parallel to or "in" the plane, we subtract
coordinates of any two pairs of the points to find two such vectors: 

%22%22=%22%22matrix%281%2C7%2C++++%22%3C%22%2C-4%2C%22%2C%22%2C3%2C%22%2C%22%2C0%2C%22%3E%22%29

%22%22=%22%22matrix%281%2C7%2C++++%22%3C%22%2C1%2C%22%2C%22%2C1%2C%22%2C%22%2C1%2C%22%3E%22%29

Now we cross those two vectors to get a vector which is perpendicular to
both those vectors, and therefore perpendicular (normal) to the plane.

matrix%281%2C7%2C++++%22%3C%22%2C-4%2C%22%2C%22%2C3%2C%22%2C%22%2C0%2C%22%3E%22%29%22%D7%22matrix%281%2C7%2C++++%22%3C%22%2C1%2C%22%2C%22%2C1%2C%22%2C%22%2C1%2C%22%3E%22%29

n = abs%28matrix%283%2C3%2Ci%2Cj%2Ck%2C-4%2C3%2C0%2C1%2C1%2C1%29%29%22%22=%22%223i%2B4j-7k%22%22=%22%22matrix%281%2C7%2C%22%3C%22%2C3%2C%22%2C%22%2C4%2C%22%2C%22%2C-7%2C%22%3E%22%29

So substituting in the point-normal equation of a plane:

a%28x-x%5B1%5D%29%2Bb%28y-y%5B1%5D%29%2Bc%28z-z%5B1%5D%29=0

3%28x-%281%29%5E%22%22%29%2B4%28y-%28-1%29%5E%22%22%29-7%28z-%28-1%29%5E%22%22%29=0

3%28x-1%29%2B4%28y%2B1%29-7%28z%2B1%29=0

3x-3%2B4y%2B4-7z-7=0

3x%2B4y-7z-6=0

Edwin