Question 108 of 480
Evaluate \(\int 2(2x - 3)^{\frac{2}{3}} \mathrm d x\)
- A. 3/5(2x-3)5/3 + k
- B. 6/5(2x-3)5/3 + k
- C. 2x-3+k
- D. 2(2x-3)+k
Correct Answer:
A
Explanation
To evaluate the integral \(\int 2(2x - 3)^{\frac{2}{3}} \mathrm{d}x\), we will use the method of substitution. Let's go through the steps in detail.
### Step 1: Choose a Substitution
We notice that the expression \(2x - 3\) is inside the power function. A good substitution would be:
\[
u = 2x - 3
\]
Now, we need to find \(\mathrm{d}u\):
\[
\mathrm{d}u = 2 \mathrm{d}x \quad \Rightarrow \quad \mathrm{d}x = \frac{1}{2} \mathrm{d}u
\]
### Step 2: Substitute in the Integral
Now we can substitute \(u\) and \(\mathrm{d}x\) into the integral:
\[
\int 2(2x - 3)^{\frac{2}{3}} \mathrm{d}x = \int 2u^{\frac{2}{3}} \left(\frac{1}{2} \mathrm{d}u\right)
\]
This simplifies to:
\[
\int u^{\frac{2}{3}} \mathrm{d}u
\]
### Step 3: Integrate
Next, we integrate \(u^{\frac{2}{3}}\):
\[
\int u^{\frac{2}{3}} \mathrm{d}u = \frac{u^{\frac{2}{3} + 1}}{\frac{2}{3} + 1} + C = \frac{u^{\frac{5}{3}}}{\frac{5}{3}} + C = \frac{3}{5} u^{\frac{5}{3}} + C
\]
### Step 4: Substitute Back
Now we substitute back \(u = 2x - 3\):
\[
\frac{3}{5} (2x - 3)^{\frac{5}{3}} + C
\]
### Final Answer
Thus, the evaluated integral is:
\[
\int 2(2x - 3)^{\frac{2}{3}} \mathrm{d}x = \frac{3}{5} (2x - 3)^{\frac{5}{3}} + C
\]
### Correct Option
The correct option is **A: \(\frac{3}{5}(2x-3)^{\frac{5}{3}} + k\)**.
### Explanation of Other Options
- **Option B: \(\frac{6}{5}(2x-3)^{\frac{5}{3}} + k\)**: This option is incorrect because it suggests that the coefficient in front of \((2x - 3)^{\frac{5}{3}}\) is \(\frac{6}{5}\), which does not match our integration result.
- **Option C: \(2x - 3 + k\)**: This option is incorrect because it does not reflect the power of \((2x - 3)\) raised to \(\frac{5}{3}\) that we obtained during integration. It also lacks the necessary coefficient.
- **Option D: \(2(2x - 3) + k\)**: This option is incorrect as it suggests a linear function rather than the correct power function we derived.
### Summary
- We used substitution to simplify the integral.
- The integral of \(u^{\frac{2}{3}}\) was calculated correctly.
- We substituted back to express the answer in terms of \(x\).
- The correct answer is \(\frac{3}{5}(2x - 3)^{\frac{5}{3}} + k\).
This method of substitution is a common technique in calculus for handling integrals involving polynomial expressions.