Question

Calculate the area enclosed between the lines \( y = 2x + 3 \) and \( y = x^2 \).

Ask by Summers Dunn. in Nigeria
Jan 21,2025

Real Tutor Solution

Tutor-Verified Answer

Answer

The area enclosed between the lines \( y = 2x + 3 \) and \( y = x^2 \) is \( \frac{32}{3} \) square units.

Solution

To find the area enclosed between the lines \( y = 2x + 3 \) and \( y = x^2 \), follow these steps: ### 1. **Find the Points of Intersection** Set the two equations equal to each other to find the points where they intersect: \[ 2x + 3 = x^2 \] Rearrange the equation: \[ x^2 - 2x - 3 = 0 \] Solve for \( x \): \[ x = \frac{2 \pm \sqrt{(-2)^2 - 4 \cdot 1 \cdot (-3)}}{2 \cdot 1} = \frac{2 \pm \sqrt{4 + 12}}{2} = \frac{2 \pm \sqrt{16}}{2} = \frac{2 \pm 4}{2} \] Thus, the solutions are: \[ x = 3 \quad \text{and} \quad x = -1 \] So, the points of intersection are at \( x = -1 \) and \( x = 3 \). ### 2. **Determine Which Function Is on Top** Choose a test point between \( x = -1 \) and \( x = 3 \) to determine which function is above the other. Let \( x = 0 \): \[ y_{\text{line}} = 2(0) + 3 = 3 \] \[ y_{\text{parabola}} = (0)^2 = 0 \] Since \( y_{\text{line}} > y_{\text{parabola}} \), the line \( y = 2x + 3 \) is above the parabola \( y = x^2 \) in this interval. ### 3. **Set Up the Integral for the Area** The area \( A \) between the two curves from \( x = -1 \) to \( x = 3 \) is: \[ A = \int_{-1}^{3} \left[(2x + 3) - x^2\right] \, dx \] ### 4. **Compute the Integral** Integrate term by term: \[ \int (2x + 3 - x^2) \, dx = \int 2x \, dx + \int 3 \, dx - \int x^2 \, dx = x^2 + 3x - \frac{x^3}{3} \] Evaluate from \( x = -1 \) to \( x = 3 \): \[ A = \left[3^2 + 3(3) - \frac{3^3}{3}\right] - \left[(-1)^2 + 3(-1) - \frac{(-1)^3}{3}\right] \] \[ A = \left[9 + 9 - 9\right] - \left[1 - 3 + \frac{1}{3}\right] = 9 - \left(-\frac{5}{3}\right) = \frac{32}{3} \] ### **Final Answer** \[ \boxed{\dfrac{32}{3}} \]

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Extra Insights

To find the area enclosed between the lines \( y = 2x + 3 \) and \( y = x^2 \), we first need to determine the points of intersection. We set the equations equal to each other: \[ 2x + 3 = x^2 \] Rearranging gives us: \[ x^2 - 2x - 3 = 0 \] Factoring the quadratic equation, we have: \[ (x - 3)(x + 1) = 0 \] This gives us the points of intersection at \( x = 3 \) and \( x = -1 \). Next, we need to find the area between the curves from \( x = -1 \) to \( x = 3 \). The area \( A \) can be calculated by the integral of the top curve minus the bottom curve: \[ A = \int_{-1}^{3} (2x + 3 - x^2) \, dx \] Now we can simplify the integrand: \[ 2x + 3 - x^2 = -x^2 + 2x + 3 \] We will compute the definite integral: \[ A = \int_{-1}^{3} (-x^2 + 2x + 3) \, dx \] Calculating the integral: \[ \int (-x^2 + 2x + 3) \, dx = -\frac{x^3}{3} + x^2 + 3x \] Next, we evaluate this from \( x = -1 \) to \( x = 3 \): \[ A = \left[ -\frac{3^3}{3} + 3^2 + 3 \cdot 3 \right] - \left[ -\frac{(-1)^3}{3} + (-1)^2 + 3(-1) \right] \] Calculating the first term: \[ -\frac{27}{3} + 9 + 9 = -9 + 18 = 9 \] Calculating the second term: \[ -\left(-\frac{-1}{3} + 1 - 3\right) = \frac{1}{3} - 2 = -\frac{5}{3} \] Now, adding these results: \[ A = 9 + \frac{5}{3} = 9 + 1.67 \approx 10.67 \] To express \( 9 + \frac{5}{3} \) as a single fraction: \[ A = \frac{27}{3} + \frac{5}{3} = \frac{32}{3} \] Thus, the area enclosed between the lines \( y = 2x + 3 \) and \( y = x^2 \) is: \[ \boxed{\frac{32}{3}} \]

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