Solve an Exponential Equation: Relating the Bases

Problem:  Solve the exponential equation.

36^{x}=(1/6)^{x-3}

Solution:

 

The exponential equation
36^{x}=(1/6)^{x-3}
The bases of the exponents on each side of the equation can be made the same.  36 can be written as 6^2 and 1/6 can be written as 6^{-1}
36^{x}=(1/6)^{x-3}
(6^2)^{x}=(6^{-1})^{x-3}

Use the power rule for exponents to multiply the exponents.
Power Rule for Exponents
(b^m)^n=b^{mn}

(6^2)^{x}=(6^{-1})^{x-3}
6^{2x}=6^{-1(x-3)}
6^{2x}=6^{-x+3}
Exponential functions are one-to-one thus giving us the property that if the bases are the same the exponents are equal.
If b^x=b^y then x=y
6^{2x}=6^{-x+3}
2x=-x+3
Solve the remaining equation.  This equation is linear, first get the variables to the same side.
2x=-x+3
2x+x=-x+x+3
3x=3 

Solve:  Get the variable by itself.
3x=3
{3x}/3={3}/3
x=1
Check: Substitute into the original equation.
36^{1}=(1/6)^{1-3}
36=(1/6)^{-2}
36=6^{2}
36=36

The solution to the equation 36^{x}=(1/6)^{x-3} is x=1.

Here is a video example of a similar type of problem.