Essential Ideas for Section 4.9

The entire section provides additional practice with Polya's problem solving procedure, which we restate here for convenience:

GUIDELINE FOR PROBLEM SOLVING
First: You have to understand the problem.
Second: Devise a plan. Find the connection between the data and the unknown. Look for patterns, relate to a previously solved problem or to a known formula, or simplify the given information to give you an easier problem.
Third: Carry out the plan.
Fourth: Look back. Examine the solution obtained.