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 However, nonspecialists (including many doctors) still tend to use an older perspective, now seen as outdated by experts.
Of the 7.3 million persons aged 12 or older classified with illicit drug dependence or abuse in 2012, 4.3 million persons had marijuana dependence or abuse.. It doesn't take a rocket scientist to figure out that the more legal and available marijuana becomes, the higher those numbers are going to go.