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# Function notation confusion watch

1. I can't seem to figure out where I'm going wrong.

Y= f(1/3 multiplied by x)
Then I'm given f(x) = x^3

I put x into the function and get x^3/3 but I'm told it should be x^3/27

Where am I going wrong.
2. (Original post by Chrollo-Lucilfer)
I can't seem to figure out where I'm going wrong.

Y= f(1/3 multiplied by x)
Then I'm given f(x) = x^3

I put x into the function and get x^3/3 but I'm told it should be x^3/27

Where am I going wrong.
If

then

Can you see why this is equal to and not ?
3. (Original post by notnek)
If

then

Can you see why this is equal to and not ?
Thanks. Can you just tell me where I go wrong on this question:

y=f(1/3 multiplied by x)
F(x) = 1/x

So I write:
1 divided by 1/3 multiplied by x
If I follow BIDMAS I get 1 x 3/1 x X

But I know the correct answer to be 3/x

So I'm curious why it's written 1/3 x X instead of just x/3?
4. (Original post by Chrollo-Lucilfer)
Thanks. Can you just tell me where I go wrong on this question:

y=f(1/3 multiplied by x)
F(x) = 1/x

So I write:
1 divided by 1/3 multiplied by x
If I follow BIDMAS I get 1 x 3/1 x X

But I know the correct answer to be 3/x

So I'm curious why it's written 1/3 x X instead of just x/3?
Just follow what Notnek did above such that

So if

then

then multiply top and bottom of the main fraction by 3

P.S. It doesn't matter whether it is written as or as they mean the exact same thing.
5. (Original post by Chrollo-Lucilfer)
Thanks. Can you just tell me where I go wrong on this question:

y=f(1/3 multiplied by x)
F(x) = 1/x

So I write:
1 divided by 1/3 multiplied by x
If I follow BIDMAS I get 1 x 3/1 x X

But I know the correct answer to be 3/x

So I'm curious why it's written 1/3 x X instead of just x/3?
I'm not sure what you mean when you say you are following BIDMAS here.

For , you could multiply top and bottom of the fraction by :

Alternatively, you could split up the fraction (reverse multiplication of fractions):

6. (Original post by notnek)
I'm not sure what you mean when you say you are following BIDMAS here.

For , you could multiply top and bottom of the fraction by :

Alternatively, you could split up the fraction (reverse multiplication of fractions):

I interpreted it as 1 divided by 1/3 multiplied by x. If I multiply 1/3 and x I get. x/3 then dividing with one I get 3/x

I mention BIDMAS because if I do division then multiplication working from left to right I get 3x.

But the way you and RDKgames explained it makes me think that I've gone completely wrong. If so what is the mistake I'm making?
7. (Original post by Chrollo-Lucilfer)
I interpreted it as 1 divided by 1/3 multiplied by x. If I multiply 1/3 and x I get. x/3 then dividing with one I get 3/x

I mention BIDMAS because if I do division then multiplication working from left to right I get 3x.

But the way you and RDKgames explained it makes me think that I've gone completely wrong. If so what is the mistake I'm making?
If you had then that would be .

But for fraction notation, you can think of the numerator and denominator as having invisible brackets around them.

So

actually means

Another example is e.g.

If you were to follow BIDMAS then you might get but there are invisible brackets so really it means

8. (Original post by notnek)
If you had then that would be .

But for fraction notation, you can think of the numerator and denominator as having invisible brackets around them.

So

actually means

Another example is e.g.

If you were to follow BIDMAS then you might get but there are invisible brackets so really it means

Thank you. That makes a lot more sense.
9. (Original post by RDKGames)
Just follow what Notnek did above such that

So if

then

then multiply top and bottom of the main fraction by 3

P.S. It doesn't matter whether it is written as or as they mean the exact same thing.
I know x/3 and 1/3 multiplied by x is equivalent. My question is why is it written is 1/3 multiplied by x instead of x/3?
10. (Original post by Chrollo-Lucilfer)
I know x/3 and 1/3 multiplied by x is equivalent. My question is why is it written is 1/3 multiplied by x instead of x/3?
No reason really. Perhaps for clarity. It's not a big deal.

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