Function Notation - Problem 3 4,408 views

Teacher/Instructor Alissa Fong
Alissa Fong

MA, Stanford University
Teaching in the San Francisco Bay Area

Alissa is currently a teacher in the San Francisco Bay Area and Brightstorm users love her clear, concise explanations of tough concepts

If a multiple choice problem asks you to determine which function represents the given table of values, start by plugging in one set of values into each function of the multiple choice items in order to being the process of elimination. Continue plugging in one set of values to each function until all but the correct function is eliminated.

As you guys know multiple choice is one of the really common methods of Math problem that you see and that's both a bonus and a curse. What I want to do is look at this function problem that's a multiple choice one. Which function best models the data and here we go. So here are function choices we want to figure out which one of these guys describes this set of numbers.

For me personally what I like to do is look at when x is zero because I think zeros are easy to work with. It's totally up to you, there's lots of different ways to approach this problem. But what I would do is I would look at that x equals 0 y equals -1 or f(x) equals -1 business and try to find out in which problem oh excuse me, in which function when I set the 2 in x equals 0 do I get the answer as -1.

Let's look at equation A, if I put it in x is 0 I'll have f(x) equals -1 times 0 is just 0, okay f(x) is 2. That cannot be the right answer because this point is not a solution it doesn't work.

Let's try B, instead of f(x) I'm going to write f(0) just to kind of show you guys using proper function notation what I'm doing instead of my x number, I'm plugging in the value 0. 2 times 0 plus 3, 2 times 0 is 0 plus 3 is 3 that's not it either. I'm looking for where I get -1.

Multiple choice not so bad, I'm already half way there. 2 times 0 take away 1 there it is 2 times 0 is 0 take away 1 so my function when I plug in 0 as my input I get the output value of -1. That's what I was looking for.

If I want to be an A plus student I can check that this letter D also does not work and you can kind of do it in your brain. If you stick 0 right there, you get 0 as your output. I was looking for -1. So this is just one way you can approach this multiple choice problem using functions and it goes pretty quickly by using the process of elimination. I picked a number for x that I wanted to work with that's an input value and then I went through and looked for where I got the corresponding output value.