Selected Applications of Quadratic Equations
1. (Choosing the solution that makes sense) A computer store manager buys several computers of the
same model for $12,000. The store can regain this $12,000 investment by selling all but two of the
computers at a profit of $200 per computer. To do this, how many computers must be sold, and at
what price?
2. (A geometry problem) An L-shaped sidewalk from the library to the gym on a high school campus
is 70 yards long. By cutting diagonally across the grass, students shorten the walking distance to
50 yards. What are the lengths of two legs of the sidewalk?
3. (Using the graph) A tennis ball is tossed vertically upward from a height of 5 feet according to the
height equation (ask your physics professor why)
h = −16t2 + 16t + 5
where h is the height of the tennis ball in feet and t is the time in seconds.
(a) After how many seconds does the tennis ball hit the ground?
(b) What is the maximum height of the ball?