# exponents

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• Apr 28th 2008, 01:49 PM
nugiboy
exponents
Basicly, ive got the following:

8^2.5 times 2^-0.5

On the mark scheme, it changes the 8^2.5 to 2^7.5

I don't understand how it does this step. Can anyone explain?
• Apr 28th 2008, 01:51 PM
Moo
Hello,

Quote:

Originally Posted by nugiboy
Basicly, ive got the following:

$\displaystyle 8^[2.5] * 2^[-0.5]$

On the mark scheme, it changes the $\displaystyle 8^[2.5]$ to $\displaystyle 2^[7.5]$

I don't understand how it does this step. Can anyone explain?

$\displaystyle 8=2^3$

And you know that $\displaystyle (a^b)^c=a^{bc}$

Plus, $\displaystyle a^b a^c=a^{b+c}$

This is all you need for getting from one formula to another.
• Apr 28th 2008, 01:53 PM
icemanfan
Quote:

Originally Posted by nugiboy
Basicly, ive got the following:

$\displaystyle 8^[2.5] * 2^[-0.5]$

On the mark scheme, it changes the $\displaystyle 8^[2.5]$ to $\displaystyle 2^[7.5]$

I don't understand how it does this step. Can anyone explain?

$\displaystyle 8^{2.5} = (2^3)^{2.5} = 2^{3\cdot{2.5}} = 2^{7.5}$

It's just rules of exponents.