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C H A P T E R 2 Polynomial and Rational Functions

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75. —CONTINUED—<br />

(d)<br />

A 8<br />

x50 x<br />

3<br />

8<br />

3 x2 50x<br />

8<br />

3 x2 50x 625 625<br />

8<br />

3 x 252 625<br />

8<br />

3 x 252 5000<br />

3<br />

The maximum area occurs at the vertex <strong>and</strong> is<br />

square feet. This happens when feet <strong>and</strong><br />

feet. The dimensions<br />

are feet by 33 feet.<br />

1<br />

50003<br />

x 25<br />

y 200 4253 1003<br />

2x 50<br />

76. (a) Radius of semicircular ends of track:<br />

Distance around two semicircular parts of track:<br />

d 2r 2 1<br />

r <br />

y y 2 1<br />

2 y<br />

77.<br />

(b) Distance traveled around track in one lap:<br />

d y 2x 200<br />

3<br />

y 200 2x<br />

y 4<br />

9 x2 24<br />

x 12<br />

9<br />

200 2x<br />

y <br />

<br />

Section 2.1 Quadratic <strong>Functions</strong> <strong>and</strong> Models 147<br />

(c) Area of rectangular region:<br />

200 2x<br />

A xy x<br />

2<br />

2<br />

2<br />

The area is maximum when <strong>and</strong><br />

200 250<br />

y 100<br />

x 50<br />

The vertex occurs at The maximum height is y3 feet.<br />

4<br />

9 32 24<br />

b 249<br />

3.<br />

3 12 16<br />

2a 249 9<br />

78. y <br />

(a) The ball height when it is punted is the y-intercept.<br />

16<br />

2025 x2 9<br />

x 1.5<br />

5<br />

y 16<br />

2025 02 9<br />

0 1.5 1.5 feet<br />

5<br />

(b) The vertex occurs at x b<br />

2a <br />

95<br />

2162025<br />

The maximum height is<br />

—CONTINUED—<br />

f 3645 16<br />

32 <br />

2025 3645<br />

32 2<br />

9<br />

5 3645<br />

32 1.5<br />

6561<br />

64<br />

6561<br />

32<br />

3645<br />

32 .<br />

1.5 6561<br />

64<br />

(e) They are all identical.<br />

feet <strong>and</strong> y 33 feet<br />

1<br />

x 25<br />

3<br />

1<br />

200x 2x2 <br />

<br />

13,122<br />

64<br />

<br />

<br />

x2 100x<br />

x2 100x 2500 2500<br />

x 502 5000<br />

<br />

96<br />

64<br />

.<br />

6657<br />

feet 104.02 feet.<br />

64

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