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 However, nonspecialists (including many doctors) still tend to use an older perspective, now seen as outdated by experts.
The effects usually stop after 3 or 4 hours. Smoking pot can increase your heart rate by as much as two times for up to 3 hours. Thatâs why some people have a heart attack right after they use marijuana. It can increase bleeding, lower blood pressure, and affect your blood sugar, too.