Math Is Fun Forum
  Discussion about math, puzzles, games and fun.   Useful symbols: ÷ × ½ √ ∞ ≠ ≤ ≥ ≈ ⇒ ± ∈ Δ θ ∴ ∑ ∫ • π ƒ -¹ ² ³ °

You are not logged in.

#1 2012-12-03 00:55:15

gbrad88
Member
Registered: 2012-12-03
Posts: 16

Solving for x

I am solving for X below:

4^(3x+5) = 1/256


The answer I get is -3 please correct me if I am wrong and why if you can please. Much appreciated.

Offline

#2 2012-12-03 00:58:52

bob bundy
Moderator
Registered: 2010-06-20
Posts: 6,259

Re: Solving for x

hi gbrad88

Welcome to the forum.

That answer looks good to me.

smile

Bob


You cannot teach a man anything;  you can only help him find it within himself..........Galileo Galilei

Offline

#3 2012-12-03 02:15:20

gbrad88
Member
Registered: 2012-12-03
Posts: 16

Re: Solving for x

Sometimes I get x = -1/3 so Im not sure whats the right way to do it. :-(

Offline

#4 2012-12-03 02:18:34

bobbym
Administrator
From: Bumpkinland
Registered: 2009-04-12
Posts: 82,779

Re: Solving for x

Hi;

You can convert that expression on the right to be

does that help you?


In mathematics, you don't understand things. You just get used to them.
I have the result, but I do not yet know how to get it.
All physicists, and a good many quite respectable mathematicians are contemptuous about proof.

Offline

#5 2012-12-03 02:23:03

gbrad88
Member
Registered: 2012-12-03
Posts: 16

Re: Solving for x

I'm not sure. I think I don't understand.

Offline

#6 2012-12-03 02:26:14

bobbym
Administrator
From: Bumpkinland
Registered: 2009-04-12
Posts: 82,779

Re: Solving for x

You now have

Here is a trick to these types whenever the bases are the same


you can ignore them and just solve the equation that you get from the exponents.


In mathematics, you don't understand things. You just get used to them.
I have the result, but I do not yet know how to get it.
All physicists, and a good many quite respectable mathematicians are contemptuous about proof.

Offline

#7 2012-12-03 05:12:01

gbrad88
Member
Registered: 2012-12-03
Posts: 16

Re: Solving for x

That trick makes a lot of sense, but, what about when one number cannot be the same? Like the 6 below:

3^x+7=6

Offline

#8 2012-12-03 05:45:38

bob bundy
Moderator
Registered: 2010-06-20
Posts: 6,259

Re: Solving for x

hi gbrad88,

I'd do it like this:

Unfortunately, that's where this question unravels because you'd need to go into complex number theory to sort out log(-1).

This sort of thing happens if you make up a question at random.  (And you thought it was easy for a teacher to throw some questions together)

Bob


You cannot teach a man anything;  you can only help him find it within himself..........Galileo Galilei

Offline

#9 2012-12-03 06:05:17

gbrad88
Member
Registered: 2012-12-03
Posts: 16

Re: Solving for x

Maybe if I re-write it.

3^(x+7)=6

Offline

#10 2012-12-03 06:12:15

bob bundy
Moderator
Registered: 2010-06-20
Posts: 6,259

Re: Solving for x

OK.  That'll do.

Bob


You cannot teach a man anything;  you can only help him find it within himself..........Galileo Galilei

Offline

Board footer

Powered by FluxBB