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Solve \(2^{6x} + 2^{3x + 2} = 21\)

 May 26, 2020
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Let   \(u=2^{3x}\)   then the equation can be rewritten as \(u^2+4u-21=0\)

 

This factorises as:  (u + 7)(u - 3) = 0

 

Can you take it from here?

 May 26, 2020

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