Math CentralQuandaries & Queries


Question from Brian, a parent:

Make an Input -output table to represent the function. Use 0,1,2,3 as the Domain.
f(x)= 3+7x

Hi Brian,

A function can be seen as a calculating device, much like some of the buttons on your calculator. You type in a number, press the appropriate button (maybe the "√" button) and the calculator displays a number. In function notation the number you type (the input) is often written as the letter x, the name of the function is "f" and the output values is f(x). In your case the output is f(x) = 3 + 7x which says "Multiply the input by 7 and then add 3." The convention is that multiplication always takes place before addition. Hence if you input number is 5 then the output is f(5) = 3 + 7 × 5 = 3 + 35 = 38.

By an input-output table you are asked to produce a table something like

x f(x)
5 38

I filled in the row corresponding to x = 5, you can complete the rest of the table.


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