For a function of two variables z=f(x,y), the gradient is the two-dimensional vector <f_x(x,y),f_y(x,y)>. This definition generalizes in a natural way to functions of more than three variables. For the function z=f(x,y)=4x^2+y^2.
By this definition, about 10% of people who smoke marijuana become addicted to it. (More on Time.com: PHOTOS â Cannabis Conventions). However, nonspecialists (including many doctors) still tend to use an older perspective, now seen as outdated by experts.
Legal marijuana supporters have argued that itâs not as addictive as other âharderâ drugs, such as heroin and cocaine. Addiction treatment specialists, however, have seen firsthand that long term use does lead to marijuana addiction. Research suggests as many as 10% of users will develop dependence over time.