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what is y in terms of x?

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by egybs » Wed Jun 11, 2008 9:03 am
First of all i think you made a mistake with the question..

I think it should be 5^x – 5^(x - 3) = (124)(5^y) If it isn't this.. it doesn't make sense.

Answer is C.

5^x – 5^(x - 3) = (124)(5^y)
5^x = 5^3 * 5^(x-3)
So:
5^(x-3)*5^3 – 5^(x - 3) = (124)(5^y)
5^(x-3)(5^3 - 1) = (124)(5^y)
5^(x-3)(124) = (124)(5^y)
Therefore:
5^(x-3) = 5^y

so y = x-3
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