Little question about exponents

Al-Allo · 2013-07-02 04:38:12

Hi,

If I had : 2^6/-2^5

How would I know if the base will keep it's negative sign or not ? Thanks

Bob · 2013-07-02 04:40:10

depends whether it says (-2)^5 or -(2^5)

Strictly, in the absence of any helpful brackets, the power takes precedence over the minus so it would be the second.

Bob

Al-Allo · 2013-07-02 04:41:52

Nah, no brackets. But I'm not sure to have understood. Will there be a negative sign or not ??? And could you explain me why ? THanks

bobbym · 2013-07-02 05:02:24

Hi;

bob bundy wrote:

depends whether it says (-2)^5 or -(2^5)

Without the brackets the minus sign stays.

I would think they would be asking the first one though.

Al-Allo · 2013-07-02 05:03:27

And why would it be that way ?

bobbym · 2013-07-02 05:13:18

Hi;

Because they love to be tricky.

If you assume the second alternative in Bob's suggestion you are asking where does the minus sign go in -2^5. The answer, nowhere!

But the other one (-2)^5 that illustrates a principle.

Bob · 2013-07-02 05:19:25

hi Al-Allo

For the rules of precedence see

http://www.mathsisfun.com/operation-order-bodmas.html

So

As it happens you would get the same result if you did (-2)^5

So here is a similar example where the denominator has an even power

Whereas

Bob

Al-Allo · 2013-07-02 05:32:39

I don't think I made it clear what I wanted, the way you showed it to me bob, that I know. But I'm talking about the rules of exponenets. ex :

2^6/-2^5 =

I know it will give me a 2^1 in my answer, but I don't know if it will stay positive or not. I could do the calculations like you did bob, but how would I know directly without doing them ?

Bob · 2013-07-02 06:02:12

Do you want to know how to use

but when one of the xs is replaced by -x

So it will depend on whether n is odd or even. odd means result will be minus. even means result will be plus.

Bob

Al-Allo · 2013-07-02 07:19:38

2^6 /-1^5 * 2^5

2^1 /-1

-2

WOuld this be correct ? (Im trying it without the brackets)

And could you show me an example where the answer would'nt be negative ? (WITHOUt brackets...thanks )

Bob · 2013-07-02 07:50:33

Yes, that looks ok to me.

Would you like to try some more, just to be sure?

Bob

Al-Allo · 2013-07-02 08:15:53

Actually, I was able to prove to myself that without brackets my answer would always be negative, no matter what. (which was the reason why I started this topic)
But yeah, a last one, just to be sure ! thank you

Bob · 2013-07-02 08:23:30

Evaluate

Bob

Al-Allo · 2013-07-02 09:25:00

{3^3*5^3} over {-3^2*5^2} rightarrow {-3*5} rightarrow =-15

Last edited by Al-Allo (2013-07-02 09:25:19)

bobbym · 2013-07-02 10:20:35

You can use codecogs to latex that expression correctly.

http://latex.codecogs.com/editor.php

Al-Allo · 2013-07-02 10:47:31

Thanks bobbym

anonimnystefy · 2013-07-02 10:55:19

That is correct!

Al-Allo · 2013-07-02 10:57:08

Ah ok, thank you!

Last edited by Al-Allo (2013-07-02 10:57:21)

Math Is Fun Forum

#1 2013-07-02 04:38:12

Little question about exponents

#2 2013-07-02 04:40:10

Re: Little question about exponents

#3 2013-07-02 04:41:52

Re: Little question about exponents

#4 2013-07-02 05:02:24

Re: Little question about exponents

#5 2013-07-02 05:03:27

Re: Little question about exponents

#6 2013-07-02 05:13:18

Re: Little question about exponents

#7 2013-07-02 05:19:25

Re: Little question about exponents

#8 2013-07-02 05:32:39

Re: Little question about exponents

#9 2013-07-02 06:02:12

Re: Little question about exponents

#10 2013-07-02 07:19:38

Re: Little question about exponents

#11 2013-07-02 07:50:33

Re: Little question about exponents

#12 2013-07-02 08:15:53

Re: Little question about exponents

#13 2013-07-02 08:23:30

Re: Little question about exponents

#14 2013-07-02 09:25:00

Re: Little question about exponents

#15 2013-07-02 10:20:35

Re: Little question about exponents

#16 2013-07-02 10:47:31

Re: Little question about exponents

#17 2013-07-02 10:55:19

Re: Little question about exponents

#18 2013-07-02 10:57:08

Re: Little question about exponents

Board footer