Question 15524
Find a vector x with ||x||=2 that has the same direction as the vector defined by the points A(3,2,1) and B(1,-1,0).
The opposite direction?
  direction of ab = i(1-3)+j(-1-2)+k(0-1) = -2i-3j-k
  vector x has sime direction .Hence vector|x|= s*(-2i-3j-k) where s is a scalar to be found ||x|| = s*||(-2i-3j-k)||=s*{{{sqrt((-2)^2+(-3)^2+(-1)^2)}}}
    s*{{{sqrt(4+9+1)}}}=s*{{{sqrt14}}}= 2...given 
   Hence s = (2/*{{{sqrt14}}})
vector |x| =  (2/*{{{sqrt14}}})*(-2i-3j-k) ....answer

if the direction is opposite then vector |x| =  (2/*{{{sqrt14}}})*(2i+3j+k)