Question 100825
8^x=(1/16)^(x-4)
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Rewrite as follows:

2^3x = 2^[-4(x-4)]
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Since the bases are the same the exponents must be equal:

3x = -4(x-4)
3x = -4x+16
7x = 16
x = 16/7
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Cheers,
Stan H.