1. Exponential equation

I've banged my head senseless on an exponential equation lately. I can't seem to solve however i try. Any help would be appreciated.

problem:

4^2x - 4^x = 8 * 4^(x+3)

solve for x

2. Hi,
Originally Posted by bael
problem:

4^2x - 4^x = 8 * 4^(x+3)

solve for x
This equation can be written $\displaystyle 4^{x}\left(4^x-1\right)=8\times 4^x\times 4^3$ and one can divide both sides by $\displaystyle 4^x$ since for all $\displaystyle x$, $\displaystyle 4^x\neq0$.

Can you take it from here ?

3. Originally Posted by bael
I've banged my head senseless on an exponential equation lately. I can't seem to solve however i try. Any help would be appreciated.

problem:

4^2x - 4^x = 8 * 4^(x+3)

solve for x

Lets assume the equation is:

$\displaystyle 4^{2x}-4^x=8 \times 4^{x+3}$

or:

$\displaystyle 4^{2x}-4^x=8 \times 4^3 \times 4^{x}$

rearrange:

$\displaystyle (4^{x})^2-513\times 4^x=4^x(4^x-513)=0$

so either $\displaystyle 4^x=0$ which is impossible or:

$\displaystyle 4^x=513$

and you should be able to finish this yourself from that.

CB

4. Originally Posted by bael
I've banged my head senseless on an exponential equation lately. I can't seem to solve however i try. Any help would be appreciated.

problem:

4^2x - 4^x = 8 * 4^(x+3)

solve for x

$\displaystyle 4^{2x}-4^x=8*4^{x+3}$

$\displaystyle 4^x*4^x-4^x=8*4^x*4^3$

$\displaystyle 4^x(4^x-1)=8*4^x*4^3$ and since $\displaystyle 4^x\not=0$ at anypoint we can divide by it

$\displaystyle 4^x-1=8*64$

you good from here?

5. thanks a lot to all of you. I think I've been everything except this solution, thank you for opening my eyes!!