math
posted by karla .
two vectors are defined as a=2i+xj and b=i4j. find value of x if
a) the vectors are parallel
b) the vectors are perpendicular

dy/dx = x/2
dy/dx = 4
if parallel x/2 = 4 so x = 8
if perpendicular x/2 =  (1/4) = 1/4
so x = 1/2