I read that y=-2x is a direct proportion graph. But how is this so? Since as one variable increases the other variable decreases proportionately so how can this be considered to be a direct proportion case? So does it mean that k>0? Since when it is less than 0 it then becomes a case which does not fit into any of the scenarios? Or if we were to write it then since it decreases proportionately then the graph would be written as y=2/x. So on the whole, will k always be positive? Thanks for the help guys!