SOLUTION: 2^2x +21=10(2^x)

Question 1061812: 2^2x +21=10(2^x)
Answer by Alan3354(69443) (Show Source): You can put this solution on YOUR website!
2^2x +21=10(2^x)
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2^(2x) - 10*2^x +21 = 0
(2^x - 3)*(2^x - 7) = 0
********* Sub u for 2^x to make it clearer.
u^2 - 10u + 21 = 0
********************************************
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2^x - 3 = 0
2^x = 3
x*log(2) = log(3)
x = log(3)/log(2) =~ 1.585
======================
2^x = 7
Do the same way.

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