Applications of Derivatives 155
8.2 Applied Maximum and Minimum Problems
Main Concepts:General Procedure for Solving Applied Maximum and Minimum
Problems, Distance Problem, Area and Volume Problem, Business
Problems
STRATEGY
General Procedure for Solving Applied Maximum
and Minimum Problems
Steps:
- Read the problem carefully, and if appropriate, draw a diagram.
- Determine what is given and what is to be found and represent these quantities by
mathematical symbols. - Write an equation that is a function of the variable representing the quantity to be
maximized or minimized. - If the equation involves other variables, reduce the equation to a single variable that
represents the quantity to be maximized or minimized. - Determine the appropriate interval for the equation (i.e., the appropriate domain for
the function) based on the information given in the problem. - Differentiate to obtain the first derivative and to find critical numbers.
- Apply the First Derivative Test or the Second Derivative Test by finding the second
derivative. - Check the function values at the end points of the interval.
- Write the answer(s) to the problem and, if given, indicate the units of measure.
Distance Problem
Find the shortest distance between the pointA(19, 0) and the parabolay=x^2 − 2 x+1.
Solution:
Step 1: Draw a diagram. (See Figure 8.2-1.)
Figure 8.2-1
Step 2: LetP(x,y) be the point on the parabola and letZrepresent the distance between
pointsP(x,y) andA(19, 0).