.
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).
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On solving exponential equations see also the lesson
- Solving exponential equations
- OVERVIEW of lessons on solving exponential equations
in this site.