Math Is Fun Forum

Natkirky

Member

Registered: 2006-10-17

Posts: 21

Help with Logs

Hi,

Can someone please show me how to work out this equation?  [exp (x+3 ln x)]² 

I have the answer but no working and I can't get to it.

Its the whole equation being raised to 2 that's getting me, can you square exp? If so how does this work.

I might be missing something really silly I'm not great with logs and keep forgetting all the different formulas.

Thank you

Bob

Administrator

Registered: 2010-06-20

Posts: 10,621

Re: Help with Logs

Hi Natkirky,

But where is the 'equals' in your equation ?

This may make it easier.

Bob

---

Children are not defined by school ...........The Fonz
You cannot teach a man anything;  you can only help him find it within himself..........Galileo Galilei
Sometimes I deliberately make mistakes, just to test you!  …………….Bob

Natkirky

Member

Registered: 2006-10-17

Posts: 21

Re: Help with Logs

Hi Bob,

The question just asks to simplify the expression.  It's using the rule e^ ln (something) = something.  I can do these but I'm stuck on the squared bracket. 

The answer is x^6 e^2x.  I hope that helps and thank you.

1a2b3c2212

Member

Registered: 2009-04-04

Posts: 419

Re: Help with Logs

e^(lnx) = x

Bob

Administrator

Registered: 2010-06-20

Posts: 10,621

Re: Help with Logs

Hi Natkirky

Start with the expression not yet squared.

split the powers:

take the '3' inside the log

but 'e' and 'ln' are inverse functions

now square the expression and re-order the terms:

Hope that helps, (but post back if any step is unclear)

Bob

---

Children are not defined by school ...........The Fonz
You cannot teach a man anything;  you can only help him find it within himself..........Galileo Galilei
Sometimes I deliberately make mistakes, just to test you!  …………….Bob

Natkirky

Member

Registered: 2006-10-17

Posts: 21

Re: Help with Logs

Hi Bob,

Thanks for your help i knew it would be something silly never thought about squaring the bracket last.

Can i just double check why e^x squared is e^2x and not e^x².

Thanks again for your help.

bobbym

bumpkin

From: Bumpkinland

Registered: 2009-04-12

Posts: 109,606

Re: Help with Logs

Hi Natkirky;

---

In mathematics, you don't understand things. You just get used to them.
If it ain't broke, fix it until it is.
Always satisfy the Prime Directive of getting the right answer above all else.

Natkirky

Member

Registered: 2006-10-17

Posts: 21

Re: Help with Logs

Hi Bob,

Thanks a lot it has taken me ages to get this I really need to start reading the questions properly!!

bobbym

bumpkin

From: Bumpkinland

Registered: 2009-04-12

Posts: 109,606

Re: Help with Logs

On behalf of bob and I you are welcome.

---

In mathematics, you don't understand things. You just get used to them.
If it ain't broke, fix it until it is.
Always satisfy the Prime Directive of getting the right answer above all else.