Math Is Fun Forum

pavino14

Member

Registered: 2017-07-09

Posts: 3

Help me on Vectors ... pls

If x=ai+bj  , y=bj+ck , z=ai +ck, for which of the following triads (a,b,c) is x perpendicular to(z-y)?

  1)  (4 ,1 ,1)
  2)  (2 ,2 ,2)
  3)  (1 ,-1 ,1)
  4)  (-1, -2, 0
  5)  (1 ,2 ,0)

zetafunc

Moderator

Registered: 2014-05-21

Posts: 2,440

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Re: Help me on Vectors ... pls

First, compute

. We see that:

Recall that two vectors are perpendicular if their dot product (also called scalar product) is zero.

So you want to show that the dot product of

with

is zero, for some choice of

. Now all you have to do is try the different possibilities given and see which one gives you

when you take the dot product.

Feel free to let us know if you need more help!