Step-by-step explanation:
8.a.
a function is something that looks like
y = ax + b or similar.
it describes the way to calculate the result for whatever input value you can come up with.
so,
C = 12×d + 8
you could also say
C(d) = 12×d + 8
as, when you rent, you have to pay these $8 in any case, no matter how long you stay, and you need to pay $12 per day you stay.
funny thing is : you understood this perfectly well when doing b.
c.
the constant rate of change is always the factor of the input variable. here : 12
it is the ratio of (y change) / (x change)
or here (C change / d change).
it indicates that for any increase of d by 1 (staying one day longer) the charges C increase by 12.
9.a.
remember, what we just said about the rate of change ?
it is (result change) / (input change).
between 2010 and 2015
the input changed by +5 (from 2010 to 2015).
the result changed by +6.25 (from 37 to 43.25).
the rate of change is therefore
6.25/5 = 1.25 = 1 1/4 = 5/4
the function is therefore
population in millions = (years since 2010)×5/4 + 37
p = y×5/4 + 37
b.
now we want to find the number of years (y) so that the result of that equation is 50.
50 = y×5/4 + 37
13 = y×5/4
52 = 5y
y = 52/5 = 10.4
so, this will be during the 11th year after 2010 = 2021.
10.
be careful and concentrate.
you see that the sequence goes up 20, when n goes up 5 (and not just 1) ? there was your initial mistake.
a.
again, remember the change rate : it is result change / input change.
so, we have here 20/5 = 4.
so,
C(n) = 4×n + 50
b.
n = 12
C(12) = 4×12 + 50 = 98
c.
now we have C(n), and want to find for which n this is true.
C(n) = 78
78 = 4×n + 50
28 = 4×n
n = 7
after 7 visits the costs are 78.
there are the basic costs of 50 (for n = 0 or 0 visits) and then extra 4 for every visit.
d.
the x-axis is for the number of visits, the y-axis for the costs.
so, the line starts at the point (0, 50), and then passes through the points of the original table (5, 70), (10, 90), (15, 110). and if you want you can calculate the points for higher x (or number of visits).
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