SOLUTION: Four raised to the power x plus 6 to the power x equals 9 to the power x

Algebra.Com
Question 1154470: Four raised to the power x plus 6 to the power x equals 9 to the power x
Answer by ikleyn(52834)   (Show Source): You can put this solution on YOUR website!
.

The given exponential equation


     +  =              (1)


is equivalent to


     +  = ,   or


     +  = .          (2) 


Introduce new variables  u = 2^x,  v = 3^x.  Then equation (2) takes the form

    u^2 + u*v = .


Divide both sides by u^2.  You will get

     -  - 1 = 0                (3)


Let z = .   Then equation (3) takes the form

    z^2 - z - 1 = 0.


Solve this quadratic equation using the quadratic formula


     =  = .


The roots are  

     = ,   and

     = .


Thus, we should consider two cases.


(a)   = .


     It means   =  = .


     Next, take any logarithm, log base 10, or natural logarithm "ln"  from both sides to continue


        = ,

        x =  /  =  = 1.1868  (approximately).


    Thus this case is completed.



(b)   = - 


     It means  -  =  = .

     
     The left side is negative, while the right side is positive.


     So, this case has no solutions.
     

ANSWER.  The original equation has only one root  x =  /  =  = 1.1868  (approximately).
Solved.



RELATED QUESTIONS

Solve the equation 3 raised to the 3x power = 9 raised to the x+1... (answered by stanbon)
7 raised to the x power parenthesis 7 raised to the 3rd power outside the parenthesis is... (answered by solver91311)
Factor the expression: {{{ x + 4X^(1/2) + 3 }}} x plus four x raised to the one half... (answered by ewatrrr)
10x to the 2nd power plus x to the 2nd power... (answered by checkley77)
169 raised to the power of 3/2 =13 raised to the power of (x-1) (answered by Alan3354,lwsshak3)
Trying to solve: 8^x^2 = 2^x+4 (8 raised to the x power which is squared equals 2 (answered by Earlsdon)
If x raised to the 27th power equals one million, what is the value of... (answered by reviewermath)
 4^x - (17 times 2^x) + 16 = 0 (let me read it to make sure: 4 raised to the x power... (answered by ankor@dixie-net.com)
X to the third power over x to the tenth power raised to the... (answered by tommyt3rd)