9.
our to
owing
a marine biologist tracked the growth of a
population of sea stars along a coast. she noted
an exponential growth pattern of the population.
in modeling the total population, p = f(t),
over time, t, which of the following should
she use as a practical domain?
a. all real numbers
b. p> 0
c. to
d. t> o

the domain of a function is the set of input values, x , for which a function is defined. the domain is shown in the left oval in the picture below. the function provides an output value, f(x) , for each member of the domain.

the revenue of the fitness center, y, is the product of two factors: the number of members and the fee paid by each member. there are 320 members now, but number of members goes down by 10 for each $5 increase in fees, so if x is the number of $5 price increases then members is equal to (320 - 10x). since the fee is currently $45, and the fee increases by $5 for every price bump x, the fee is given by (45 + 5x). so, revenue y is given by y = (320 - 10x)(45 + 5x).