Vectors?!?!?

Given: a − b = c and c = h54, 36i.


Which of the following expressions is NOT


meaningful?


1. (c · a) − |b|


2. a · (b · c)


3. (c · a)b


4. c · (a + b)


5. 20(c · a)b





Thanks for looking. I am not exactly sure what is meant by "meaningless" any help would be appreciated.

Vectors?!?!?
Meaningless means that the operation is not defined in a vector space.





1. c*a = the dot product of two vectors is a number; the magnitude of a vector is also a number, so 1 is defined.


2. The dot product only exist between vector...you cannot take a dot product of a vector and a number...meets the meaningless criteria.


3. The scalar multiplication exist...product is defined.


4. dot product of the vector c and the vector resulting from the sum of a+b is defined.


5. And, from all of the above, 5 is a defined quality.





Your job know is to make the appropriate substitutions and solve. Good luck.
Reply:a, b, and c are all vectors.





2. a · (b · c) is not meaningful.


(b . c) is a scalar. So you can't take the dot product of a vector a and a scalar. A dot product is between two vectors.