Question

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

Ask by Harmon Wade. in Saudi Arabia
Jan 24,2025

Real Tutor Solution

Tutor-Verified Answer

Answer

The area 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 \( x \)-values where they intersect: \[ 2x + 3 = x^2 \] Rearrange the equation: \[ x^2 - 2x - 3 = 0 \] Solve the quadratic equation: \[ x = \frac{2 \pm \sqrt{4 + 12}}{2} = \frac{2 \pm \sqrt{16}}{2} = \frac{2 \pm 4}{2} \] \[ x = 3 \quad \text{and} \quad x = -1 \] 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 \( x = 3 \), say \( x = 0 \): \[ y_1 = 2(0) + 3 = 3 \] \[ y_2 = (0)^2 = 0 \] Since \( y_1 > y_2 \) at \( x = 0 \), \( y = 2x + 3 \) is the upper function between \( x = -1 \) and \( x = 3 \). 3. **Set Up the Integral for the Area:** The area \( A \) between the curves from \( x = -1 \) to \( x = 3 \) is: \[ A = \int_{-1}^{3} \left( (2x + 3) - x^2 \right) \, dx \] Simplify the integrand: \[ A = \int_{-1}^{3} (-x^2 + 2x + 3) \, dx \] 4. **Integrate and Evaluate:** Find the antiderivative: \[ \int (-x^2 + 2x + 3) \, dx = -\frac{x^3}{3} + x^2 + 3x \] Evaluate from \( x = -1 \) to \( x = 3 \): - At \( x = 3 \): \[ -\frac{3^3}{3} + 3^2 + 3(3) = -9 + 9 + 9 = 9 \] - At \( x = -1 \): \[ -\frac{(-1)^3}{3} + (-1)^2 + 3(-1) = \frac{1}{3} + 1 - 3 = -\frac{5}{3} \] Subtract the lower limit from the upper limit: \[ A = 9 - \left( -\frac{5}{3} \right) = 9 + \frac{5}{3} = \frac{32}{3} \] 5. **Conclusion:** The area enclosed between the lines \( y = 2x + 3 \) and \( y = x^2 \) is: \[ \boxed{\dfrac{32}{3}} \]

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To find the area enclosed between the lines \( y = 2x + 3 \) and \( y = x^2 \), we first need to determine the points where they intersect. Setting the two equations equal to each other gives: \[ 2x + 3 = x^2 \] Rearranging this into standard form results in: \[ x^2 - 2x - 3 = 0 \] Factoring the quadratic equation yields: \[ (x - 3)(x + 1) = 0 \] The solutions are \( x = 3 \) and \( x = -1 \). These are the x-coordinates of the points of intersection. Next, we need to set up the integral to calculate the area between the curves from \( x = -1 \) to \( x = 3 \). The area \( A \) can be calculated as follows: \[ A = \int_{-1}^{3} ((2x + 3) - (x^2)) \, dx \] Now, we calculate the integral: \[ A = \int_{-1}^{3} (2x + 3 - x^2) \, dx \] \[ = \int_{-1}^{3} (-x^2 + 2x + 3) \, dx \] Calculating the antiderivative: \[ = \left[ -\frac{x^3}{3} + x^2 + 3x \right]_{-1}^{3} \] Now, we evaluate at the upper limit \( x = 3 \): \[ = \left( -\frac{3^3}{3} + 3^2 + 3 \times 3 \right) = \left( -9 + 9 + 9 \right) = 9 \] Next, we evaluate at the lower limit \( x = -1 \): \[ = \left( -\frac{(-1)^3}{3} + (-1)^2 + 3(-1) \right) = \left( \frac{1}{3} + 1 - 3 \right) = \left( \frac{1}{3} - 2 \right) = \left( \frac{1}{3} - \frac{6}{3} \right) = -\frac{5}{3} \] Now, we subtract the lower limit evaluation from the upper limit evaluation: \[ A = 9 - \left(-\frac{5}{3}\right) = 9 + \frac{5}{3} = \frac{27}{3} + \frac{5}{3} = \frac{32}{3} \] Thus, the area enclosed between the lines \( y = 2x + 3 \) and \( y = x^2 \) is: \[ \frac{32}{3} \text{ square units.} \]

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