Hey there! Sign in to join this conversationNew here? Join for free
Turn on thread page Beta
    • Thread Starter
    Offline

    9
    ReputationRep:
    Hi,

    I would appreciate it if someone could explain what the significance and use of the 'f of x' notation is, particularly in graphs?
    Is it just an alternative way of writing 'y' in e.g. y=2x+9?

    Thanks
    Offline

    15
    ReputationRep:
    (Original post by AKRYL)
    Hi,

    I would appreciate it if someone could explain what the significance and use of the 'f of x' notation is, particularly in graphs?
    Is it just an alternative way of writing 'y' in e.g. y=2x+9?

    Thanks
    f(x) means 'function of x'

    You are correct in saying that an alternative of y=2x+9\
    is f(x)=2x+9

    you can use anything;

    g(x),\  h(x) etc
    • Thread Starter
    Offline

    9
    ReputationRep:
    (Original post by edothero)
    f(x) means 'function of x'

    You are correct in saying that an alternative of y=2x+9\
    is f(x)=2x+9

    you can use anything;

    g(x), \ h(x)
    Unparseable or potentially dangerous latex formula. Error 6: Image was not produced or one of its dimensions is too small.
    \
    etc
    Can you elaborate on what you mean by 'function of x'?
    Offline

    22
    ReputationRep:
    (Original post by AKRYL)
    Hi,

    I would appreciate it if someone could explain what the significance and use of the 'f of x' notation is, particularly in graphs?
    Is it just an alternative way of writing 'y' in e.g. y=2x+9?

    Thanks
    Yeah, pretty much, f of x means function of x as someone else said previously.

    It means that your rule that maps x \mapsto 2x+9 is a function/rule that sends your x value to another value using a certain rule.

    With this, you can then see that f(x) = 2x + a is a function of x and so a is a constant, or other such subtleties.
    Offline

    15
    ReputationRep:
    (Original post by AKRYL)
    Can you elaborate on what you mean by 'function of x'?
    f(x)=2x+9

    f(x) essentially means, when x goes in, f(x) comes out

    Its a function with a set 'criteria' if you'd like.

    For this particular function:

    x \rightarrow 2x \rightarrow (2x+9)
    As input x goes in, it gets multiplied by 2, followed by an addition of 9, then outputs f(x)

    So when x=5,

    (5) \rightarrow 2(5) \rightarrow [2(5)+9]

    f(x)=19

    Like I said before, this could easy be g(x) which again represents 'g is a function of x'
    Don't be thrown off by the f.
    • Thread Starter
    Offline

    9
    ReputationRep:
    (Original post by Zacken)
    Yeah, pretty much, f of x means function of x as someone else said previously.

    It means that your rule that maps x \mapsto 2x+9 is a function/rule that sends your x value to another value using a certain rule.

    With this, you can then see that f(x) = 2x + a is a function of x and so a is a constant, or other such subtleties.
    So is '2x+9' the rule that is applied to the value contained within the brackets of f(x) in order to give you the value of y?
    • Thread Starter
    Offline

    9
    ReputationRep:
    (Original post by edothero)
    f(x)=2x+9

    f(x) essentially means, when x goes in, f(x) comes out

    Its a function with a set 'criteria' if you'd like.

    For this particular function:

    x \rightarrow 2x \rightarrow (2x+9)
    As input x goes in, it gets multiplied by 2, followed by an addition of 9, then outputs f(x)

    So when x=5,

    (5) \rightarrow 2(5) \rightarrow [2(5)+9]

    f(x)=19

    Like I said before, this could easy be g(x) which again represents 'g is a function of x'
    Don't be thrown off by the f.
    So is '2x+9' the rule or set of instructions that is applied to the value contained within the brackets of f(x) ,in order to give you the value of y?
    Offline

    15
    ReputationRep:
    (Original post by AKRYL)
    So is '2x+9' the rule that is applied to the value contained within the brackets of f(x) in order to give you the value of y?
    Yes, that is correct

    The 2x+9 is applied to the input.

    So for example

    f(2) = 2(2)+9

    \therefore f(2) = 13

    y = 13

    So you would know that when x=2, y=13
    And you can plot that easily.
    Offline

    1
    ReputationRep:
    (Original post by AKRYL)
    Hi,

    I would appreciate it if someone could explain what the significance and use of the 'f of x' notation is, particularly in graphs?
    Is it just an alternative way of writing 'y' in e.g. y=2x+9?

    Thanks
    f(x) notation essentially shows the input value for x (or whatever letter chosen to represent the variable of the equation)
    E.g.
    y=x+69
    f(-4)=-4+69-->when x=-4, y=65
    • Thread Starter
    Offline

    9
    ReputationRep:
    (Original post by edothero)
    Yes, that is correct

    The 2x+9 is applied to the input.

    So for example

    f(2) = 2(2)+9

    \therefore f(2) = 13

    y = 13
    Ok, but what does the 'f' part of 'f(x)' represent?
    Also, why is that when you write the equation of a curve, using this notation, you have to write the part highlighted in bold y=f(x)=2x+3 and not simply f(x)=2x+3?
    Offline

    15
    ReputationRep:
    (Original post by AKRYL)
    Ok, but what does the 'f' part of 'f(x)' represent?
    Also, why is that when you write the equation of a curve, using this notation, you have to write the part highlighted in bold y=f(x)=2x+3?
    Nothing important , its just a way of labeling the function.

    You could do

    f(x) = 2x+9
    g(x) = 2x+9
    h(x) = 2x+9


    It all means the same thing.
    • TSR Support Team
    Offline

    21
    ReputationRep:
    TSR Support Team
    (Original post by AKRYL)
    Ok, but what does the 'f' part of 'f(x)' represent?
    Also, why is that when you write the equation of a curve, using this notation, you have to write the part highlighted in bold y=f(x)=2x+3 and not simply f(x)=2x+3?
    The function. What everyone else has been trying to explain.

    The f(x) is just the name of the function you could use any letter instead of f to indicate a different function, where you have two. So  f(x) = 3x^2 and g(x) = 2x-1
    Offline

    11
    ReputationRep:
    (Original post by AKRYL)
    Ok, but what does the 'f' part of 'f(x)' represent?
    Also, why is that when you write the equation of a curve, using this notation, you have to write the part highlighted in bold y=f(x)=2x+3 and not simply f(x)=2x+3?
    To clarify further, f is the function and we write f(x) to be the value of the function at x. So technically f(x) isn't the function it's the value of the output of the function when the input is x.
    Offline

    3
    ReputationRep:
    Correct me if I'm wrong but a function is like a rule which affects any value of the independent variable (which is x here).
 
 
 
Reply
Submit reply
Turn on thread page Beta
Updated: October 31, 2015
Poll
“Yanny” or “Laurel”
Useful resources

Make your revision easier

Maths

Maths Forum posting guidelines

Not sure where to post? Read the updated guidelines here

Equations

How to use LaTex

Writing equations the easy way

Student revising

Study habits of A* students

Top tips from students who have already aced their exams

Study Planner

Create your own Study Planner

Never miss a deadline again

Polling station sign

Thinking about a maths degree?

Chat with other maths applicants

Can you help? Study help unanswered threads

Groups associated with this forum:

View associated groups

The Student Room, Get Revising and Marked by Teachers are trading names of The Student Room Group Ltd.

Register Number: 04666380 (England and Wales), VAT No. 806 8067 22 Registered Office: International House, Queens Road, Brighton, BN1 3XE

Write a reply...
Reply
Hide
Reputation gems: You get these gems as you gain rep from other members for making good contributions and giving helpful advice.