A level maths help!!

If you have -4^n-1 and you need to take logs, can you take the negative sign from -4 out so it would result in -log(4)^n-1= n-1-log(4)?

Or will it be log(-4)^n-1? But then you can't take the log of a negative number

Reply 1

mqb2766

21

Original post by Idk131

If you have -4^n-1 and you need to take logs, can you take the negative sign from -4 out so it would result in -log(4)^n-1= n-1-log(4)?

Or will it be log(-4)^n-1? But then you can't take the log of a negative number

If would probably be best to post the full question and your working.
Either you know that the result is positive or ... ?

Original post by Idk131

If you have -4^n-1 and you need to take logs, can you take the negative sign from -4 out so it would result in -log(4)^n-1= n-1-log(4)?

Or will it be log(-4)^n-1? But then you can't take the log of a negative number

-4^(n-1) is always negative

You cant take log of it.

OP

Nevermind I got it

Original post by RDKGames

-4^(n-1) is always negative

- 4 x -4 =

Reply 5

Notnek

21

Original post by Idk131

If you have -4^n-1 and you need to take logs, can you take the negative sign from -4 out so it would result in -log(4)^n-1= n-1-log(4)?

Or will it be log(-4)^n-1? But then you can't take the log of a negative number

Your post is filled with ambiguous notation e.g. -4^n-1 could mean a variety of things but it looks like you meant -4^(n-1).

Please use more brackets in future.

Original post by Muttley79

- 4 x -4 =

+16

and -4 x 4 = …

(edited 1 year ago)

Reply 7

Muttley79

20

Original post by RDKGames

+16

and -4 x 4 = …

Irrelevant - you said it was always negative!

Reply 8

Notnek

21

Original post by Muttley79

Irrelevant - you said it was always negative!

-4^(n-1) is always negative. Maybe you misread his post?

Reply 9

Muttley79

20

Original post by Notnek

-4^(n-1) is always negative. Maybe you misread his post?

Not if he meant (-4)^ (n-1) - the OP's notation is all over the place.

Original post by Notnek

-4^(n-1) is always negative. Maybe you misread his post?

I don’t know what’s going on here but I suspect they will next tell me that bananas are vegetables.

Reply 11

davros

16

Original post by Idk131

If you have -4^n-1 and you need to take logs, can you take the negative sign from -4 out so it would result in -log(4)^n-1= n-1-log(4)?

Or will it be log(-4)^n-1? But then you can't take the log of a negative number

To avoid ambiguity in future, could you use brackets as appropriate, or use Latex to format the expression, or at least take a picture of the question / mark scheme you're looking at? No-one is sure what you mean by -4^n-1. Is it supposed to be

-4^{n-1}

(-4)^{n-1}

-4^n - 1

(-4)^n - 1

or something else?!

Thanks :smile:

A level maths help!!

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