# Exponent confusion.

1. Feb 21, 2015

### Benthal

My TI-89 calculator rearranged $$2^{2m+1}-1$$ to $$2\times 4^m - 1$$
I can't for life of me work out how it did it. Is anybody able to put me out of my misery?

Ben

2. Feb 21, 2015

### Mentallic

It used two exponent rules:

$$\left(a^b\right)^c=a^{bc}$$

$$a^{b+c}=a^ba^c$$

So start by using the second to get rid of that pesky +1 in $2^{2m+1}$

3. Feb 21, 2015

### Benthal

Oh god! Of course. I must not be feeling well.

Thanks.