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Preeeeeetika
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PareshGmat
\(5^x – 5^{(x- 3)} = 124*5^y\)

Re-write as

\(5^x – 5^{(x- 3)} = (125 - 1 ) * 5^y\)

\(5^x – 5^{(x- 3)} = 125* 5^y - 5^y\)

\(5^x – 5^{(x- 3)} = 5^{(y+3)} - 5^y\)

LHS = RHS, so equating the powers

y = x+3 ; Answer = C

Hi PareshGmat,
I don't understand how equating the powers in the last part makes y = x+3. Could you please kindly explain.

Edit: i just noticed. think you wrote it wrong the answer should be y= x-3 not y = x+1
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If we take x = 3, it becomes
\(5^3 – 5^{(3- 3)} = 124*5^y\)
\(5^3 – 5^0 = 124*5^y\)
\(125 – 1 = 124*5^y\)
\(124 = 124*5^y\)
\(5^y = 1\)
y = 0

Substituting x = 3, we get y = 0 for C
alltimeacheiver
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
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Hello from the GMAT Club BumpBot!

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