Question 39 of 480
Find the area bounded by the curve y = x(2-x). The x-axis, x = 0 and x = 2.
- A. 4 sq units
- B. 2 sq units
- C.
4
3
squnits
4
3
𝑠
𝑞
𝑢
𝑛
𝑖
𝑡
𝑠
- D.
1
3
squnits
1
3
𝑠
𝑞
𝑢
𝑛
𝑖
𝑡
𝑠
Correct Answer:
C
Explanation
To find the area bounded by the curve \( y = x(2-x) \), the x-axis, and the vertical lines \( x = 0 \) and \( x = 2 \), we will follow these steps:
### Step 1: Understand the Curve
The equation \( y = x(2-x) \) is a quadratic function. We can rewrite it in standard form:
\[
y = -x^2 + 2x
\]
This is a downward-opening parabola. The roots of the equation (where the curve intersects the x-axis) can be found by setting \( y = 0 \):
\[
x(2-x) = 0
\]
This gives us \( x = 0 \) and \( x = 2 \). Thus, the curve intersects the x-axis at these points.
### Step 2: Determine the Area
The area under the curve from \( x = 0 \) to \( x = 2 \) can be found using definite integration. The area \( A \) is given by:
\[
A = \int_{0}^{2} y \, dx = \int_{0}^{2} (x(2-x)) \, dx
\]
### Step 3: Set Up the Integral
Now we set up the integral:
\[
A = \int_{0}^{2} (2x - x^2) \, dx
\]
### Step 4: Calculate the Integral
We can calculate the integral step by step:
1. **Integrate the function**:
\[
\int (2x - x^2) \, dx = x^2 - \frac{x^3}{3} + C
\]
2. **Evaluate the definite integral from 0 to 2**:
\[
A = \left[ x^2 - \frac{x^3}{3} \right]_{0}^{2}
\]
Now, we calculate the upper limit:
\[
A = \left(2^2 - \frac{2^3}{3}\right) - \left(0^2 - \frac{0^3}{3}\right)
\]
\[
= \left(4 - \frac{8}{3}\right) - 0
\]
\[
= 4 - \frac{8}{3} = \frac{12}{3} - \frac{8}{3} = \frac{4}{3}
\]
### Step 5: Final Answer
Thus, the area bounded by the curve, the x-axis, and the lines \( x = 0 \) and \( x = 2 \) is:
\[
\boxed{\frac{4}{3}} \text{ square units}
\]
### Explanation of Other Options
- **Option A (4 sq units)**: This option is incorrect because it does not account for the shape of the parabola and the area under it. The area is not a rectangle or a simple shape that would yield 4 square units.
- **Option B (2 sq units)**: This option is also incorrect. While it might seem plausible, the area calculated through integration shows that the area is less than 2 square units.
- **Option D (1/3 sq units)**: This option is incorrect as well. The area calculated is significantly larger than this value.
### Common Pitfalls
- **Misunderstanding the shape**: Students may visualize the area incorrectly, thinking it is larger than it is due to the curve's height.
- **Incorrect integration**: Failing to properly integrate the function or miscalculating the definite integral can lead to wrong answers.
- **Forgetting to evaluate at both limits**: Always remember to substitute both limits when calculating definite integrals.
### Revision Summary
- The area under the curve \( y = x(2-x) \) from \( x = 0 \) to \( x = 2 \) is found using definite integration.
- The correct area is \( \frac{4}{3} \) square units.
- Always evaluate the integral at both limits to find the area accurately.
- Be cautious of the shape of the curve and ensure proper integration techniques are applied.