Julissa is running a 10-kilometer race at a constant pace. After running for 18 minutes, she completes 2 kilometers. After runni
2 answers:
For this case, the first thing we must do is define variables.
We have then:
t: the time in minutes
k: the number of kilometers
The relationship between both variables is direct.
Therefore, the function is:
Where, "c" is a constant of proportionality.
To determine "c" we use the following data:
After running for 18 minutes, she completes 2 kilometers.
Substituting values:
Clearing c we have:
Then, the equation is given by:
Answer:
An equation that can be used to represent k, the number of kilometers Julissa runs in t minutes is:
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(a) Suppose 
is a solution for this recurrence, with 
. Then
So we expect a general solution of the form
With
, we get four equations in four unknowns:
So the particular solution to the recurrence is
(b) Let
be the generating function for 
. Multiply both sides of the recurrence by 
and sum over all 
.
From here you would write each term as a power series (easy enough, since they're all geometric or derived from a geometric series), combine the series into one, and the solution to the recurrence will be the coefficient of, ideally matching the solution found in part (a).
So we expect a general solution of the form
With
So the particular solution to the recurrence is
(b) Let
From here you would write each term as a power series (easy enough, since they're all geometric or derived from a geometric series), combine the series into one, and the solution to the recurrence will be the coefficient of