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| Question 205335:  Hi all, I asked this question recently, but did not get a response. Hopefully someone can help me this time. I need to Determine whether the the two planes; 4x+y-z = 3 and 2x - 5y + 3z =2 are parallel, orthogonal, conincident or none of these.
 Steps and notes on how to solve would be very helpful.
 Thanks, -nick
 Answer by Alan3354(69443)
      (Show Source): 
You can put this solution on YOUR website! Determine whether the the two planes; 4x+y-z = 3 and 2x - 5y + 3z =2 are parallel, orthogonal, conincident or none of these. -------
 4x + y - z = 3
 Its normal vector, A, is 4i + j - k
 r = sqrt(16+1+1) = 3sqrt(2)
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 2x - 5y + 3z =2
 Its normal vector, B, is 2i - 5j + 3k
 r = sqrt(4+25+9) = sqrt(38)
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 Finding the angle between them will clarify it.
 A dot B = |A||B|cos
 A dot B = 8-5-3 = 0
 Since the magnitudes of both A and B are non-zero, the cos = 0.
 --> 90º orthogonal
 
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