yego.me
💡 Stop wasting time. Read Youtube instead of watch. Download Chrome Extension

Evaluating composite functions: using tables | Mathematics III | High School Math | Khan Academy


3m read
·Nov 11, 2024

  • [Voiceover] So we have some tables here that give us what the functions f and g are when you give it certain inputs. So, when you input negative four, f of negative four is 29. That's going to be the output of that function. So we have that for both f and g, and what I want to do is evaluate two composite functions. I want to evaluate f of g of zero, and I want to evaluate g of f of zero.

So like always, pause the video and see if you can figure it out. Let's first think about f of g of zero. F of g of zero. What is this all about? Actually let me use multiple colors here. F of g of zero. Well, this means that we're going to evaluate g at zero, so we're gonna input zero into g. Do it in that. So we're gonna input zero into our function g, and we're going to output, whatever we output is going to be g of zero. I'll write it right over here, and then we're going to input that into our function f. We're going to input that into our function f, and whatever I output then is going to be f of g of zero. F of g of zero. F of g of zero. I wrote these small here so we have space for the actual values.

So first let's just evaluate, and if you are now inspired, pause the video again and see if you can solve it. Although, if you solved it the first time, you don't have to do that now. What's g of zero? Well, when we input x equals zero, we get g of zero is equal to five. So g of zero is five. So that is five. So we're now going to input five into our function f. We're essentially going to evaluate f of five. So when you input five into our function. I'm gonna do it in this brown color. When you input x equals five into f, you get the function f of five is equal to 11. So this is going to be 11.

So, f of g of zero is equal to 11. Now, let's do g of f of zero. So now let's evaluate. I'll do this is different colors. G, maybe I'll use those same two colors actually. So now we're going to evaluate g of f of zero. G of f of zero, and the key realization is you wanna go within the parenthesis. Evaluate that first so then you can evaluate the function that's kind of on the outside.

So here we're going to take zero as an input into the function f, and then whatever that is, that f of zero, we're going to input into our function g. We're going to input into our function g, and what we're going to be, and then the output of that is going to be g of f of zero. So, let's see, what is f of zero? You see over here when our input is zero, this table tells us that f of zero is equal to one. So f of zero is equal to one. F of zero is equal to one.

So now we use one as an input into g. We're now evaluating g of one, or I can just write this. This is the same thing as g of one. G of one. Once again, why was that? 'Cause f of zero is equal to, f of zero is equal to one. And let me, I wrote those parenthesis too far away from the g. This is the same thing as g of one. Because once again f of zero is one.

Now what is g of one? Well, when I input one into our function g, I get g of one is equal to eight. So this is going to be equal, this is equal to eight, and we're done. And notice these are different values, because these are different composite functions. F of g of zero is 11, and g of f of zero is eight.

More Articles

View All
Failure of Reconstruction | AP US History | Khan Academy
How do you define freedom? Stop for a minute and picture what it means to be free. What comes into your mind? Traveling wherever you please? Having enough money to do what you want? Or is freedom better defined by what it’s not: not having anyone telling …
The insanely scary "Tailless Whip Scorpion" - Smarter Every Day 77
Are you about to grab that with your mother? What the quick? Oh golly, what is this? Call the tailless whip. Let’s whip scorpion. Let me grab it with my hand. It’s fighting them. It’s fighting! Oh fighting! What is going on? Describe what you’re feeling.…
15 Things Rich People Advise But Never Do
Everyone looks for advice from the rich, but advice is not universally applicable, and even they don’t follow it, and for good reason. Here are 15 things rich people advise but never actually do. Welcome to Alux. Number one: go to school. Going to school…
The Case of the Early Bird | Teacher Resources | Financial Literacy | Khan Academy
The name’s Duction, Detective Duction. I’m a private eye, and my eye is pointed straight at Monetary Mysteries. Love them! Financial Tom Foolery, dollar double dealing—that’s my wheelhouse, and no mistake. There’s one case I keep coming back to, turning …
Can We Fix Climate Change? | Explorer
We can’t really fix climate change. We can mitigate it. We can get to work on it. We can spread it out. We can make things better. What we got to do is stop burning fossil fuels immediately, as soon as we possibly can. Then there’s a strange effect that …
The Lost City of Chan Chan | Lost Cities with Albert Lin
I’m headed to the lost city of Chanchan, once the beating heart of the mighty Chimu Empire. Is that a pyramid? I think that’s a pyramid, a pyramid at Chanchan. Can I find answers inside the city walls as to why the children had to die? Built over a thousa…