How do you tell if a graph shows direct variation?

1 Answer
Apr 20, 2015

A graph shows direct variation if it goes through the origin, #(0,0)#. The equation is #y=kx#, where #k# is a constant, which is apparent when we write the equation as #y/x=k#. In slope-intercept form, the equation would be #y=mx+b#, where #m=k#, and #b=0#.

Lets suppose that #k=m=2#. The slope-intercept form would be #y=2x+0#. The following is the graph for this equation.
graph{y=2x+0 [-10, 10, -5, 5]}