Question

The function ​f(x)​ is the total amount spent at a store, when purchasing x items that are $5 each and the items are not taxable.

What is the practical domain for the function f(x)?



all positive integers

all real numbers

all whole numbers

all positive integers that are multiples of 5

Answer 1

f(x)=5x

normal domain: all real numbers
practical domain: all positive integers

becasue we can substituent with any positive integer in the place of x

Answer 2

First lets write out this function to get a better grasp of what x values, (domain) would apply.


f(x)=5x

The key word here is practical, a negative amount of items does not make sense so we can cross, whole numbers and real numbers off the list.

Positive integers that are multiples of 5 does not make sense, why would a shopper be restricted to buying items in pairs of five?


The most logical and only choice left is all positive integers.