how much money should i donate to khan?

However much or little you feel you can give. Thanks for considering donating!

Why domain is independent & range is dependent?

Domain is the set of input values for the function. Range is the set of output values. An input value goes into the function, then the function does whatever steps specified by the function to create the output. If you use a different input, then you will likely get a different output (depending upon the function). So, the output is dependent upon what you use for an input value. Hope this helps.

How did Sal come up with "if x is 0 then y is 3 if x is 1 then y is 5" i just want to know if its some kind of calculation or trial and error or something. (at 1:18)

Hi, I do like your question, even I got a question with it,so a function can only have one output, if you want it to be linear function yes that would not work, but he is correct, one input can only have one output, it dose not have to be a constant rate

How do you get the equation set up

Just get two or three values for x and y that fit the equation and then just extend the graph/line.

I dont get that you have the y is doubled like when you said X is 1 so that means Y is 5

y is doubled because the problem said that y is equal to three more than TWICE the value of x. The twice part tells us that x has to be multliplied by 2. y = 3 + 2x y = 3 + 2( 1 ) y = 3 + 2 y = 5

Is x=y a funtional relationship?

Yes it is. Every value of x will create only one y-value. So, it meets the definition of a function.

Is the following is a function? {0,1,2,3,4,0}

You are not really giving enough information here, this is just a set of values I don't know what it is. Now if it was x values or the domain you could see that an x value repeats (0) so it wouldn't be a function.

Main content

Algebra 1

Course: Algebra 1 > Unit 8

Lesson 7: Recognizing functions

Recognizing functions from verbal description

Name: Recognizing functions from verbal description
Uploaded: 2013-06-04T19:20:54Z
Description: Checking whether y can be described as a function of x if y is always three more than twice x.

Google Classroom

Checking whether y can be described as a function of x if y is always three more than twice x. Created by Sal Khan.

Want to join the conversation?

Sort by:

Sharan Salian
Posted 3 years ago. Direct link to Sharan Salian's post “Why domain is independent...”
Why domain is independent & range is dependent?
Button navigates to signup pageButton navigates to signup page
(6 votes)
Answer
- Kim Seidel
  Posted 3 years ago. Direct link to Kim Seidel's post “Domain is the set of inpu...”
  Domain is the set of input values for the function.
  Range is the set of output values.
  An input value goes into the function, then the function does whatever steps specified by the function to create the output. If you use a different input, then you will likely get a different output (depending upon the function). So, the output is dependent upon what you use for an input value.
  Hope this helps.
  Button navigates to signup page
  (12 votes)
RatQUEEN69
Posted 3 years ago. Direct link to RatQUEEN69's post “how much money should i d...”
how much money should i donate to khan?
Button navigates to signup pageComment on RatQUEEN69's post “how much money should i d...”
(7 votes)
Answer
- Evan
  Posted 3 years ago. Direct link to Evan's post “However much or little yo...”
  However much or little you feel you can give. Thanks for considering donating!
  Button navigates to signup page
  (6 votes)
iShowRizz
Posted 3 years ago. Direct link to iShowRizz's post “How did Sal come up with ...”
How did Sal come up with "if x is 0 then y is 3 if x is 1 then y is 5" i just want to know if its some kind of calculation or trial and error or something. (at
1:18
)
Button navigates to signup pageComment on iShowRizz's post “How did Sal come up with ...”
(5 votes)
Answer
- Eashwer Valliapan Latchumana
  Posted 3 years ago. Direct link to Eashwer Valliapan Latchumana's post “Hi, I do like your questi...”
  Hi, I do like your question, even I got a question with it,so a function can only have one output, if you want it to be linear function yes that would not work, but he is correct, one input can only have one output, it dose not have to be a constant rate
  Button navigates to signup page
  (5 votes)
kayla.smoyer
Posted 3 years ago. Direct link to kayla.smoyer's post “How do you get the equati...”
How do you get the equation set up
Button navigates to signup pageButton navigates to signup page
(5 votes)
Answer
- omgoyalmahaan
  Posted 2 years ago. Direct link to omgoyalmahaan's post “Just get two or three val...”
  Just get two or three values for x and y that fit the equation and then just extend the graph/line.
  Button navigates to signup page
  (3 votes)
mvcoichy25
Posted 6 years ago. Direct link to mvcoichy25's post “Is the following is a fun...”
Is the following is a function?
{0,1,2,3,4,0}
Button navigates to signup pageComment on mvcoichy25's post “Is the following is a fun...”
(0 votes)
Answer
- Bradley Reynolds
  Posted 6 years ago. Direct link to Bradley Reynolds's post “You are not really giving...”
  You are not really giving enough information here, this is just a set of values I don't know what it is. Now if it was x values or the domain you could see that an x value repeats (0) so it wouldn't be a function.
  Comment on Bradley Reynolds's post “You are not really giving...”
  (11 votes)
Armand van Tonder
Posted 6 years ago. Direct link to Armand van Tonder's post “In the above example func...”
In the above example function, y = 3 + 2x, if the y was squared, would it no longer be a function? What if there was, in addition to the y, also a y^2?
Button navigates to signup pageButton navigates to signup page
(4 votes)
Answer
Cian Knight
Posted 9 years ago. Direct link to Cian Knight's post “What is a function anyway...”
What is a function anyway?
Button navigates to signup pageComment on Cian Knight's post “What is a function anyway...”
(2 votes)
Answer
- Noor
  Posted 3 years ago. Direct link to Noor's post “A function is something t...”
  A function is something that will take an input, and it will do something to that input, to produce an output.
  
  Example y = f(x)
  
  In this example, y is equal to a function applied to x.
  Button navigates to signup page
  (1 vote)
adeleonfrazier
Posted 9 years ago. Direct link to adeleonfrazier's post “I dont get that you have...”
I dont get that you have the y is doubled like when you said X is 1 so that means Y is 5
Button navigates to signup pageButton navigates to signup page
(1 vote)
Answer
- Pooja Suganthan
  Posted 9 years ago. Direct link to Pooja Suganthan's post “y is doubled because the ...”
  y is doubled because the problem said that y is equal to three more than TWICE the value of x. The twice part tells us that x has to be multliplied by 2.
  y = 3 + 2x
  y = 3 + 2( 1 )
  y = 3 + 2
  y = 5
  Comment on Pooja Suganthan's post “y is doubled because the ...”
  (3 votes)
Ignacia Frost
Posted 9 years ago. Direct link to Ignacia Frost's post “I still didn't get it, I ...”
I still didn't get it, I watched the video like a thousand times. I didn't get the concept!
Button navigates to signup pageComment on Ignacia Frost's post “I still didn't get it, I ...”
(2 votes)
Answer
- Agent Smith
  Posted 9 years ago. Direct link to Agent Smith's post “You are a function. You l...”
  You are a function. You listened to the video (input), you processed it and you responded (output).
  You know y = 2x. This means give x a value and y will be double of x e.g. if x = 2,
  y = 2 × 2 = 4.
  A function is just a different way of expressing this.
  Instead of y, we write f(x) which is read f of x (please verify)
  So y =2x becomes f(x) = 2x
  Input x and get output f(x) which basically says multiply x by 2.
  Comment on Agent Smith's post “You are a function. You l...”
  (1 vote)
Ashton Tang
Posted 6 years ago. Direct link to Ashton Tang's post “Is x=y a funtional relati...”
Is x=y a funtional relationship?
Button navigates to signup pageButton navigates to signup page
(1 vote)
Answer
- Kim Seidel
  Posted 6 years ago. Direct link to Kim Seidel's post “Yes it is. Every value o...”
  Yes it is. Every value of x will create only one y-value.
  So, it meets the definition of a function.
  Button navigates to signup page
  (2 votes)

Video transcript

The value of y is always 3 more than twice x. So we can say that y is equal to 3 more than twice x. So it's 3 plus 2x is another way of saying this first sentence. So is y a function of x? So whenever you're asked whether something is a function of something else, you're really just saying, look, for any input x, does it map to exactly one y? So if we say y is a function of x, in order for this to be a function for any x that you input into this function, you must get exactly one y. So if you input an x you must get exactly one y value. If you got two values, then it's no longer a function. For any input, you get exactly one y. You could have two inputs that get to the same y, but you can't have one input that results in two different outputs. You don't know what the function is valued at at that input. Now, here it looks pretty clear that for any input, you get exactly one output. Any input uniquely determines which y. It's not like if you put an x in here, you're not sure what y is going to be. You know what y is going to be. If x is 0, y is 3. If x is 1, y is 5. And so this is definitely a function of x. y is definitely a function of x.