Answer:
C
Step-by-step explanation:
Direct variation is a special case of first order equations; in both cases, the input is multiplied by a constant which we call the "slope" or "constant of variation." However, no direct variation equation includes a constant ("y-intercept"). So, if a given equation does have a y-intersect, that equation does not represent direct variation; if it does NOT have a y-intercept, that equation represents direct variation.
A) involves a constant term, -2; NOT direct variation
B) involves a constant term, 10; NOT direct variation
C) Here 3y = x, or y = x/3, involves no constant term, so Does represent direct variation
D) involves a constant term -3; NOT direct variation
