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Homework Help: Vector perpendicular to the plane

  1. May 9, 2010 #1
    For what value of a is the vector v=(-2,1,a) perpendicular to the plane z=6x-3y+4?

    i looked the book and my teacher's solution they are different so i just want to make sure i did this right.....

    Vector v is perpendicular to the plane if it is parallel to the plane’s normal vector. A vector which is normal (= perpendicular) to the plane is n=(6,-3, 4) Hence, v parallel n if their coordinates are proportional, i.e. −2/6=1/3=a/4, therefore a=4/3

    can someone correct me if i am wrong?????????????PLZ
  2. jcsd
  3. May 10, 2010 #2


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    You got one component of the normal vector wrong.
  4. May 10, 2010 #3
    how??? z=6x-3y+4 don't u just take the coefficient and that is your normal vector?
  5. May 10, 2010 #4
    Do you see a 4z in your equation?
  6. May 10, 2010 #5
    aw crap so is it -1 then?
    Last edited: May 10, 2010
  7. May 10, 2010 #6
    since i have two vectors why can't i do Vector1 . Vector2=0?
    since the dot product says a.b=0 is perpendicular to each other?
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