* Site-Outage Notice: Our engineering elves will be tweaking the Shmoop site from Monday,
December 22 10:00 PM PST to Tuesday, December 23 5:00 AM PST. The site will be unavailable during this time.

Remember that "derivative" means "slope." Since a straight line has a constant slope (the slope is the same everywhere), the slope of the line is the derivative of the line. In this case, f(x) = 4x + 2 has a slope of 4, therefore f'(x) = 4.