Question
1. \( y=\frac{1}{2 x-1} \quad y=0 \quad x=1 \quad x=5 \quad s=? \)
Ask by Pearson Collins. in Mongolia
Mar 13,2025
Upstudy AI Solution
Tutor-Verified Answer
Answer
The area \( s \) is \( \ln 3 \).
Solution
We need to find the area \( s \) of the region bounded by the curve
\[
y = \frac{1}{2x-1},
\]
the line
\[
y=0,
\]
and the vertical lines
\[
x=1 \quad \text{and} \quad x=5.
\]
**Step 1. Set Up the Integral**
The area \( s \) is given by the integral
\[
s=\int_{x=1}^{x=5} \frac{1}{2x-1}\,dx.
\]
**Step 2. Use a Substitution**
Let
\[
u=2x-1.
\]
Then the differential \( du \) is
\[
du=2\,dx \quad\Longrightarrow\quad dx=\frac{du}{2}.
\]
We also need to change the limits:
- When \( x=1 \):
\[
u=2(1)-1=1.
\]
- When \( x=5 \):
\[
u=2(5)-1=9.
\]
**Step 3. Rewrite and Evaluate the Integral**
Substitute into the integral:
\[
s=\int_{u=1}^{u=9} \frac{1}{u}\cdot\frac{du}{2} = \frac{1}{2}\int_{u=1}^{u=9}\frac{du}{u}.
\]
The integral \( \int \frac{du}{u} \) is the natural logarithm:
\[
\int_{u=1}^{u=9}\frac{du}{u} = \ln|u|\Big|_{1}^{9} = \ln(9) - \ln(1).
\]
Since \( \ln(1)=0 \), we have:
\[
\int_{u=1}^{u=9}\frac{du}{u} = \ln 9.
\]
Thus, the area is
\[
s=\frac{1}{2}\ln 9.
\]
**Step 4. Simplify the Result**
We can simplify the result by recognizing that
\[
\frac{1}{2}\ln 9 = \ln\left(9^{\frac{1}{2}}\right)=\ln 3.
\]
**Final Answer**
\[
s = \ln 3.
\]
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Bonus Knowledge
To find the area \( s \) between the curves \( y = \frac{1}{2x-1} \) and \( y = 0 \) from \( x = 1 \) to \( x = 5 \), you first note that the function \( y \) is positive in this interval. Now, you calculate the integral: \[ s = \int_{1}^{5} \frac{1}{2x-1} \, dx. \] The integral of \( \frac{1}{2x-1} \) is \( \frac{1}{2} \ln |2x-1| \). Evaluating the definite integral gives: \[ s = \left[ \frac{1}{2} \ln |2x-1| \right]_{1}^{5} = \frac{1}{2} \ln |9| - \frac{1}{2} \ln |1| = \frac{1}{2} \ln 9 = \frac{1}{2} \cdot 2 \ln 3 = \ln 3. \] Thus, the area \( s \) is \( \ln 3 \).