Question 147049
a)Point in the same direction means the vectors are scaled versions of each other. 
In other words, the x components are in the same proportion as the y components.
{{{4/k=(-3)/(-6)}}}
{{{k=8}}}
b)Perpendicular vectors have a dot product equal to zero. 
A:[4,-3]
B:[k,-6]
{{{A*B=4*k+(-3)(-6)=0}}}
{{{4*k+18=0}}}
{{{4*k=-18}}}
{{{k=-18/4}}}
{{{k=-9/2}}}

{{{drawing( 300, 300, -6, 6, -6, 6,grid( 1 ),blue(line(0,0,-4.5,-6)),green(line( 0,0, 4, -3)))}}}
Graphical check of the answer.