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semi-simple exponent question--i'm confused!

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by tohellandback » Tue Jun 09, 2009 10:40 pm
3^x-3^x-1=162
3^(x-1)*(3-1)=162
3^(x-1)=81
x-1=4
x=5

5*4=20
The powers of two are bloody impolite!!
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by sarang » Tue Jun 09, 2009 11:04 pm
tohellandback wrote:3^x-3^x-1=162
3^(x-1)*(3-1)=162
3^(x-1)=81
x-1=4
x=5

5*4=20
hey, thanks for the response. however I do not understand still.

to re-clarify: the question had 3 raised to x subtracting 3 raised to the x minus 1.
x^3 - 3^(x-1)

I do not understand how you got ...*(3-1)... what happened to the base of 3 and the exponent "x"?

its probably a really simple concept, its just i'm very rusty...i really appreciate your help!
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by tohellandback » Tue Jun 09, 2009 11:09 pm
it is 3^x and not x^3

now what I have done is taken 3^x-1 common from both terms.
3*3*(x-1)=3^(1+x-1) (its a property, remember? if not, I would suggest you better go through it. shouldn't take more than 10 minutes)

so we are left with
3^(x-1){3-1}

Hope I helped.
Thanks
The powers of two are bloody impolite!!
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by sarang » Tue Jun 09, 2009 11:29 pm
tohellandback wrote:it is 3^x and not x^3

now what I have done is taken 3^x-1 common from both terms.
3*3*(x-1)=3^(1+x-1) (its a property, remember? if not, I would suggest you better go through it. shouldn't take more than 10 minutes)

so we are left with
3^(x-1){3-1}

Hope I helped.
Thanks
Thanks for your help. I found another way to do the problem at this link.
https://gmat.meetup.com/51/messages/boar ... 4#21137332

I appreciate it!
/s
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