A direct variation suggest that the value of x in the equation would greatly affect the value of y such that when x is increasing, y also increases and the other way around. The equation for a direct variation is that, y = kx Substituting the given values in the ordered pair, 5 = k(4) ; k = 5/4
where we pick the solution for this system such that . Then we find
Note that you can always find a solution to the system above that satisfies as long as . What this means is that you can always find the value of as a (constant) function of .