Solving Logarithmic Equations
Solving Logarithmic Equations
Example
Question
Solve for \(p\):
\[18 \log{p} - 36 = 0\]Make \(\log p\) the subject of the equation
\begin{align*} 18 \log{p} - 36 &= 0 \\ 18 \log{p} &= 36 \\ \cfrac{18 \log{p}}{18} &= \cfrac{36}{18} \\ \therefore \log{p} &= 2 \end{align*}Change from logarithmic form to exponential form
\begin{align*} \log{p} &= 2 \\ \therefore p &= 10^{2} \\ &= 100 \end{align*}Write the final answer
\(p = 100\)
Example
Question
Solve for \(n\) (correct to the nearest integer):
\[(\text{1.02})^{n} = 2\]Change from exponential form to logarithmic form
\begin{align*} (\text{1.02})^{n} &= 2 \\ \therefore n &= \log_{\text{1.02}}{2} \end{align*}Use a change of base to solve for \(n\)
\begin{align*} n &= \cfrac{\log{2}}{\log{\text{1.02}}} \\ \therefore n &= \text{35.00} \ldots \end{align*}Write the final answer
\(n = 35\)
This lesson is part of:
Functions III
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