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Unformatted text preview: 6 We have already seen the graph of this function. It was used as an example in Section 1.7 to show how the
graphing calculator can be misleading. 2.3 Quadratic Functions 149 7. The two towers of a suspension bridge are 400 feet apart. The parabolic cable7 attached to
the tops of the towers is 10 feet above the point on the bridge deck that is midway between
the towers. If the towers are 100 feet tall, ﬁnd the height of the cable directly above a point
of the bridge deck that is 50 feet to the right of the left-hand tower.
8. What is the largest rectangular area one can enclose with 14 inches of string?
9. Solve the following quadratic equations for the indicated variable.
(a) x2 − 10y 2 = 0 for x
(b) y 2 − 4y = x2 − 4 for x (e) y 2 − 3y = 4x for y (c) x2 − mx = 1 for x 7 (d) −gt2 + v0 t + s0 = 0 for t (Assume g = 0.)
(f) y 2 − 4y = x2 − 4 for y The weight of the bridge deck forces the bridge cable into a parabola and a free hanging cable such as a power
line does not form a parabola. We shall see in Exercise 13 in Section 6.5...
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