Answer:
9a. 0.8
9b. f(t) = 400(0.8^t)
10. B, C, E
Step-by-step explanation:
The growth factor (or factor of decrease) for a time period will be found by taking the ratio of the value at the end of the time period to the beginning value.
9a.
The population is 320 after 1 year. It started at 400 at the beginning of the year, so the factor of decrease is 320/400 = 0.80.
b.
The exponential function can be written as ...
f(t) = a·b^t . . . . . where 'a' is the initial population, and 'b' is the factor of decrease
The initial population is shown on the graph as 400; the factor of decrease is what we just computed.
f(t) = 400(0.80^t)
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10.
An exponential function is one that has the independent variable as an exponent. That form is seen in selections B, C, E.