I need help understanding why the following is not linearly dependent

a=$\displaystyle \left[ \begin{array}{cccr}4\\1\\3\\\end{array} \right]$

b=$\displaystyle \left[ \begin{array}{cccr}2\\-1\\3\\\end{array} \right]$

c=$\displaystyle \left[ \begin{array}{cccr}-4\\2\\6\\\end{array} \right]$

Can someone explain the concepts on how to determined if it is linear independent or linear dependent?

P.S