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Amtrak s annual passenger revenue for the years 1980 2000 is modeled approximately by the formula R = -40 |x - 11| + 990 where R is the annual revenue in millions of dollars and x is the number of years since January 1, 1980. In what years was the passenger revenue $790 million?

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Answer:

1986, 1996

Step-by-step explanation:

       Given, Annual passenger revenue for the years 1980 to 2000 id=s modeled with the formula [tex]R=-40|x-11|+990[/tex].

Here, [tex]R[/tex] is the annual revenue in millions of dollars, [tex]x[/tex] is the number of years since January 1, 1980.

       Revenue in a year was $ 790 million.

So, [tex]R=790\\-40|x-11|+990=790\\40|x-11|=200\\|x-11|=5\\x-11=5\text{ (or) }x-11=-5\\x=16\text{ (or) }x=6[/tex]

       So, after 6 yrs and 16 yrs from January 1, 1980, the Passenger revenue equals $ 790 million.

∴ Passenger revenue equals $ 790 million in 1986 and 1996.

Solving the absolute value equation, it is found that the passenger's revenue was of $790 million in 1986 and in 1996.

The solution of the absolute value equation [tex]|x| = a[/tex] is given by: [tex]x = a[/tex] or [tex]x = -a[/tex].

In this problem, the revenue in x years after 1980, in millions of dollars, is given by:

[tex]R(x) = -40|x - 11| + 990[/tex]

The passenger's revenue is of $790 million when:

[tex]R(x) = 790[/tex]

Then:

[tex]790 = -40|x - 11| + 990[/tex]

[tex]-40|x - 11| = -200[/tex]

[tex]|x - 11| = \frac{-200}{-40}[/tex]

Negative divided by negative is positive, thus:

[tex]|x - 11| = 5[/tex]

Which means that:

[tex]x - 11 = 5 \rightarrow x = 16[/tex]

Or

[tex]x - 11 = -5 \rightarrow x = 6[/tex]

Thus, the passenger's revenue was of $790 million in 1986 and in 1996.

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