So let's go here. Now, change in concentration of final minus change in concentration of initial gives you negative k times t final because this guy becomes zero. Now let's bring the initial over to this side and we get concentration of our final equals negative k times t final plus our initial concentration of x. And notice that this equation has the same form as y equals MX plus b. This is our general equation for a line. And that means if we plot this guy, we will get a line.