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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