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Appendix C C-13<br />
(a) The two data points in the previous figure show world wind-energy generating<br />
capacity for the years 1985 and 1998. What is the slope of the line<br />
joining the two points? What are the units for the slope?<br />
(b) Find the equation of the line joining the two given points. Write the answer<br />
in the form y mt b.<br />
(c) Use the result in part (b) to estimate the years in which world wind-energy<br />
generating capacity was between 3000 megawatts and 7500 megawatts<br />
(inclusive). Hint: You need to solve the inequality 3000 y 7500;<br />
round the answers to the nearest integers.<br />
(d) Your estimates in part (c) are based on the assumption that world<br />
wind-energy generating capacity increased in a straight-line fashion from<br />
1985 to 1998. By using techniques from statistics (and more detailed<br />
data), it can be shown that a more accurate summary of world wind-energy<br />
generating capacity over these years is given by the equation<br />
(e)<br />
(f)<br />
y 6.977t 3 64.786t 2 325.4t 1012<br />
where again, t 0 corresponds to 1985. Using this expression for y, estimate<br />
the years in which world wind-energy generating capacity was between<br />
3000 megawatts and 7500 megawatts (inclusive). (Round the key<br />
numbers to the nearest integers.) Compare your results to those in part (c).<br />
Although increasing rapidly, wind-energy generation is currently but a<br />
small portion of the world energy picture. For instance, whereas world<br />
wind-energy generating capacity in 1998 was 9600 megawatts, the corresponding<br />
figure for nuclear energy in 1998 was 343,000 megawatts. When<br />
might wind-energy reach this level? Use the equation in part (d) to obtain<br />
one possible answer to this question. Round your answer to the nearest five<br />
years. Hint: In an appropriate viewing rectangle, you want to look for<br />
the point where the curve y 6.977t 3 64.786t 2 325.4t 1012 meets<br />
the horizontal line y 343,000.<br />
Rework part (e), but instead of using the cubic equation from part (d),<br />
use the straight-line equation obtained in part (b). Compare the results;<br />
which scenario do you think is more realistic?