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Help for Exercises 53-58 on page 601
For Exercise 53, you are asked to find the width of the telescope's dish. According to the sketch provided, the
width of the dish is represented by the distance along the x-axis from the left x-intercept to the right
x-intercept. Using the symmetry of the parabola, find the distance from the origin to one x-intercept,
then multiply by 2. Set y = 0 and use the zero-product property to find the location of either intercept.
For Exercise 54, use the fact that the center of the dish is located on the y-axis where x is
equal to zero.
For Exercises 55-58, the parabolas are symmetric with respect to the y-axis. This means that the
vertex, and corresponding minimum or maximum, is located on the y-axis (where x = 0). Symmetry with
respect to the y-axis also helps you determine the distance from the leftmost x-intercept to the rightmost
x-intercept. Also keep in mind the direction in which the parabolas are facing and check that your answers make
sense.
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