Chapter 5: Exercises with Solutions

Chapter 5Quadratic FunctionsThis is a quadratic function and we can graph it. We enter it into our calculator usingx’s instead of t’s. A good window to use is Xmin = 0, Xmax = 10, Y min = −100and Y max = 400. We only need to look at time greater than or equal to zero.To find when the ball hits the ground (the zero of the function) with your calculator,press 2nd TRACE to access the CALC menu and choose 2:zero.Use the left arrowto move the cursoralong the curve untilit is to the left of thefirst zero. Hit ENTER.Use the right arrow tomove the cursor until itis to the right of thesame zero. Hit ENTER.Finally hit ENTERnear that same zerofor the guess, andyou get the zero.We get (7.895781, 0).Now sketch the graph on your paper.400y (ft)y=50+120t−16t 2t (s)0 (7.895781,0) 10−100Finally, we verify the time it takes the ball to hit the ground with the quadratic formula.The ball is on the ground when its height is y = 0 ft. So, set y = 0 and solve theequation.y = −16t 2 + 120t + 500 = −16t 2 + 120t + 50This is a quadratic equation with a = −16, b = 120 and c = 50. So, the solutions are,Version: Fall 2007