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Solving Exponential Equations with Different Bases




 
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Videos, worksheets, games and activities to help PreCalculus students learn how to solve exponential equations with different bases.

How to solve exponential equations with different bases?
Sometimes we are given exponential equations with different bases on the terms. In order to solve these equations we must know logarithms and how to use them with exponentiation. We can access variables within an exponent in exponential equations with different bases by using logarithms and the power rule of logarithms to get rid of the base and have just the exponent.

How to solve exponential equations using logarithms?
1. Isolate the exponential part of the equation. If there are two exponential parts put one on each side of the equation.
2. Take the logarithm of each side of the equation.
3. Solve for the variable.
4. Check your solution graphically.

Example:
Solve the exponential equations. Round to the hundredths if needed.
(a) 7x - 1 = 4
(b) 3•2x - 2 = 13
(c) (2/3)x = 53 - x
(d) 5x - 3 = 32x + 1 How to solve exponential equations with different bases?
When it's not convenient to rewrite each side of an exponential equation so that it has the same base, you do the following:
1) Take the log (or ln) of both sides
2) Apply power property
3) Solve for the variable
Example:
Solve for x.
a) 6x = 42
b) 7x = 20
c) 82x - 5 = 5x + 1
d) 3x = 5x - 1



How to use change of base formula to solve basic exponential equations?
Example:
Solve by writing as a log equation and then using the change of base formula. Round to 4 decimal places.
a) 5x = 476
b) 4•3x = 984 How to solve exponential and logarithmic equations?
Principle used: logaag(x) = g(x)
Examples:
1. Solve for x: 88x + 7 = 9
2. Solve for x:
a) 61 - 2x = 3
b) 1 + 3(42x + 3) = 8
3. Solve for x: log24x + log2x = 2
4. Solve for x:
a) log35 + log2(x + 4) = 2
b) log4x + log4(x + 3) = 1


 
How to solve exponential equations that are not one-to-one?
Examples:
34x - 5 = 17

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