Unformatted text preview: 80. The predicted annual energy usage of
the US in 2010 is approximately 112.980 Quads. 2.5 Regression 173 5. To predict when the annual US energy usage will reach 120 Quads, we substitute y = 120
into the equation of the line of best ﬁt to get 120 = 1.287x − 2473.908. Solving for x yields
x ≈ 2015.454. Since the regression line is increasing, we interpret this result as saying the
annual usage in 2015 won’t yet be 120 Quads, but that in 2016, the demand will be more
than 120 Quads. Our next example gives us an opportunity to ﬁnd a nonlinear model to ﬁt the data. According to
the National Weather Service, the predicted hourly temperatures for Painesville on March 3, 2009
were given as summarized below.
Time Temperature, ◦ F
To enter this data into the calculator, we need to adjust the x values, since just entering the
numbers could cause confusion. (Do you see why?) We have a few options available to us. Perhaps
the easiest is to...
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