SOLUTION: If 4^x+2(2^x)=80 what is the value of x?

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Question 1104176: If 4^x+2(2^x)=80 what is the value of x?
Answer by ikleyn(52839)   (Show Source): You can put this solution on YOUR website!
.
= 80

Introduce new variable u = .  Then your original equation becomes this quadratic equation

 = 0.


To solve, factor left side

(u-8)*(u+10) = 0.


It has the roots  u = 8  and  u = -10.


So, according our substitution,

    = 8  with the solution x = 3,

or

    = -10,  which has no solutions.


Answer.  The solution is x = 3.



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