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If 5x – 5x - 3 = (124)(5y), what is y in terms of x? A. x B. x - 6 C. x - 3 D. 2x + 3 E. 2x + 6 Answer:

Question should read:

If 5^x – 5^(x- 3) = 124*5^y, what is y in terms of x? A. x B. x - 6 C. x - 3 D. 2x + 3 E. 2x + 6

\(5^x-5^{x-3}=124*5^y\) --> factor out \(5^{x-3}\): \(5^{x-3}(5^3-1)=124*5^y\) --> \(5^{x-3}=5^y\) --> bases are equal so we can equate the powers: \(y=x-3\).

Answer: C.

alltimeacheiver format the questions correctly. _________________

If 5x – 5x - 3 = (124)(5y), what is y in terms of x? A. x B. x - 6 C. x - 3 D. 2x + 3 E. 2x + 6 Answer:

Question should read:

If 5^x – 5^(x- 3) = 124*5^y, what is y in terms of x? A. x B. x - 6 C. x - 3 D. 2x + 3 E. 2x + 6

\(5^x-5^{x-3}=124*5^y\) --> factor out \(5^{x-3}\): \(5^{x-3}(5^3-1)=124*5^y\) --> \(5^{x-3}=5^y\) --> bases are equal so we can equate the powers: \(y=x-3\).

Answer: C.

alltimeacheiver format the questions correctly.

Hi Bunuel, I', trying to understand your factorization, but I find some troubles when I have to factorize some value with exponent an expression like in the question (x-3 or x+4), Could you explain me that or do you have a deck where I could dive into this argument? Thank you in advance

If 5x – 5x - 3 = (124)(5y), what is y in terms of x? A. x B. x - 6 C. x - 3 D. 2x + 3 E. 2x + 6 Answer:

Question should read:

If 5^x – 5^(x- 3) = 124*5^y, what is y in terms of x? A. x B. x - 6 C. x - 3 D. 2x + 3 E. 2x + 6

\(5^x-5^{x-3}=124*5^y\) --> factor out \(5^{x-3}\): \(5^{x-3}(5^3-1)=124*5^y\) --> \(5^{x-3}=5^y\) --> bases are equal so we can equate the powers: \(y=x-3\).

Answer: C.

alltimeacheiver format the questions correctly.

Hi Bunuel, I', trying to understand your factorization, but I find some troubles when I have to factorize some value with exponent an expression like in the question (x-3 or x+4), Could you explain me that or do you have a deck where I could dive into this argument? Thank you in advance

Re: If 5^x – 5^(x- 3) = 124*5^y, what is y in terms of x? [#permalink]
28 Mar 2015, 22:00

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Re: If 5^x – 5^(x- 3) = 124*5^y, what is y in terms of x? [#permalink]
29 Mar 2015, 07:10

Expert's post

alltimeacheiver wrote:

If 5^x – 5^(x- 3) = 124*5^y, what is y in terms of x?

A. x B. x - 6 C. x - 3 D. 2x + 3 E. 2x + 6

Given that 5^x – 5^(x- 3) = 124*5^y So, 5^(x-3+3) - 5^(x- 3) = 124*5^y So, 5^(x-3) [5^3 - 1] = 124*5^y So, 5^(x-3)*124 = 124*5^y So, 5^(x-3) = 5^y So, x-3 = y

If 5^x – 5^(x- 3) = 124*5^y, what is y in terms of x? [#permalink]
07 Aug 2015, 16:29

ok this is how you solve this

you have 5^x -5^x-3 = (124) (5^y) step 1: 5^x (1-5^-3) =(124) (5^y) Step 2: 5^x(1 - 1/5^3) = (124) (5^y) Step 3: 5^x(1- 1/125) = (124) (5^y) Step 4: 5^x (125-1)/125 = (124) (5^y) Step 5: 5^x (124/125) = (124) (5^y) Step 6: 5^x =[(124) (5^y) (125) ]/124 Step 7: 5^x = (125) (5^y) Step 8: 5^x = 5^3 (5^y) Step 9: x = 3 +y --> y = x -3 for explaining purposes I broke it down in to 9 steps. It should not take you more than 5 steps to solve this in term of y.

gmatclubot

If 5^x – 5^(x- 3) = 124*5^y, what is y in terms of x?
[#permalink]
07 Aug 2015, 16:29

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