Solving Exponential Equations
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GRE Quantitative Reasoning › Solving Exponential Equations
Find one possible value of , given the following equation:
Cannot be determined from the information given.
Explanation
We begin with the following:
This can be rewritten as
Recall that if you have two exponents with equal bases, you can simply set the exponents equal to eachother. Do so to get the following:
Solve this to get t.
Solve for .
Explanation
The first step is to make sure we don't have a zero on one side which we can easily take care of:
Now we can take the logarithm of both sides using natural log:
Note: we can apply the Power Rule here
Solve for :
Explanation
Step 1: Rewrite the right side as a power of :
Step 2: Rewrite the original equation:
Step 3: Since the bases are equal, I can set the exponents equal.
So,
Solve for .
Explanation
Before beginning to solve for , we need
to have a coefficient of
:
Now we can take the natural log of both sides:
Note:
Solve this exponential equation for
Explanation
Isolate the variable by dividing by 6.
is the same as
.
Find one possible value of , given the following equation:
Cannot be determined from the information given.
Explanation
We begin with the following:
This can be rewritten as
Recall that if you have two exponents with equal bases, you can simply set the exponents equal to eachother. Do so to get the following:
Solve this to get t.
Explanation
To solve, use the natural .
Solve:
Explanation
Step 1: Rewrite the right hand side of the equation as a power of 2.
. To get this, divide the base by 2 and multiply that 2 to the exponent...
Step 2: Equate the left and right side together
We have the same base, so we equate the exponents together..
...
Explanation
Isolate by adding to both sides of the exponential equation.
Take the common log.
Use logarithmic rule 3. An exponent inside a log can be moved outside as a multiplier.
Simplify. Because
Isolate the variable by subtracting from both sides.
Solve for :
Explanation
Step 1: Write as
...
Step 2: Rewrite as
in the original equation..
Step 3: By a rule of exponents, I can set the exponents equal if the bases of both exponents are the same...
So,