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Re: a problem

by logitech » Wed Nov 12, 2008 10:43 am
elimenda wrote:if 3^6x= 8100, what is the value of (3^x-1)^3?
= (3^x-1)^3
= 3^3x-3

= 3^3X / 3^3 (i)

3^6x= 8100

3^3x = 90 (ii)

If we combine (i) + (ii)

= 3^3X / 3^3


= 90/27

= 10/3
LGTCH
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by jnellaz » Wed Nov 12, 2008 12:54 pm
Thanks Logitech. I hate to be a stickler for detail but I am really trying hard to understand and implement each of the rules for exponents correctly. (Unfortunately, I don't have 4 years of engineering!) You posted

= (3^x-1)^3
= 3^3x-3

Isn't (3^x-1)^3 equal to (3^3x-1^3 )
= (3^3x-1)

Please let me know where I went wrong. As always, thanks!
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soln

by iamcste » Wed Nov 12, 2008 1:49 pm
jnellaz wrote:Thanks Logitech. I hate to be a stickler for detail but I am really trying hard to understand and implement each of the rules for exponents correctly. (Unfortunately, I don't have 4 years of engineering!) You posted

= (3^x-1)^3
= 3^3x-3

Isn't (3^x-1)^3 equal to (3^3x-1^3 )
= (3^3x-1)

Please let me know where I went wrong. As always, thanks!

Rule is ( a^m)^n=a^mn

Applying to above e.g

means x-1=m, 3=n, a=3

hence m.n=3x-3

hence a^mn== 3^3x-3
you dont need engineering for this..just get rules and u will be all set

hence (3^x-1)^3 not equal to (3^3x-1^3 ) but equal to 3^3x-3
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by jnellaz » Wed Nov 12, 2008 3:07 pm
No...sorry. My mistake. I read this problem completely wrong.

I thought the equation above (3^x-1)^3 was ((3^x) minus 1)^3
NOT (3 to the power of (x-1))^3. A small error in interpretation.
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Re: a problem

by cartera » Sun Nov 23, 2008 8:34 am
Hi Logitech

In the point II, how did you get 3^3x=90?

logitech wrote:
elimenda wrote:if 3^6x= 8100, what is the value of (3^x-1)^3?
= (3^x-1)^3
= 3^3x-3

= 3^3X / 3^3 (i)

3^6x= 8100

3^3x = 90 (ii)

If we combine (i) + (ii)

= 3^3X / 3^3


= 90/27

= 10/3
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Re: a problem

by logitech » Sun Nov 23, 2008 8:45 am
cartera wrote:Hi Logitech

In the point II, how did you get 3^3x=90?

logitech wrote:
elimenda wrote:if 3^6x= 8100, what is the value of (3^x-1)^3?
= (3^x-1)^3
= 3^3x-3

= 3^3X / 3^3 (i)

3^6x= 8100

3^3x = 90 (ii)

3^6x= 8100 (TAKE SQUARE ROOT OF BOTH SIDES)

and you will get:

3^3x = 90 (ii)

If we combine (i) + (ii)

= 3^3X / 3^3


= 90/27

= 10/3
LGTCH
---------------------
"DON'T LET ANYONE STEAL YOUR DREAM!"
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