Math Problem Statement

use a double integral find the area bounded by y = x^2, x - y = 3, x = -3, and x = 2

Solution

To find the area bounded by the curves y=x2y = x^2, xy=3x - y = 3, x=3x = -3, and x=2x = 2 using a double integral, we follow these steps:

  1. Identify the region:

    • The curve y=x2y = x^2 is a parabola opening upwards.
    • The line xy=3x - y = 3 can be rewritten as y=x3y = x - 3.
    • We need to find the intersection points of y=x2y = x^2 and y=x3y = x - 3.
  2. Find intersection points: Set x2=x3x^2 = x - 3: x2x+3=0.x^2 - x + 3 = 0. The discriminant is: D=(1)2413=112=11.D = (-1)^2 - 4 \cdot 1 \cdot 3 = 1 - 12 = -11. Since D<0D < 0, there are no real intersections.

    We will instead check the boundaries set by x=3x = -3 and x=2x = 2.

  3. Determine the bounds of integration:

    • For x=3x = -3, y=(3)2=9y = (-3)^2 = 9.
    • For x=2x = 2, y=22=4y = 2^2 = 4.
  4. Set up the double integral: The area AA can be found using: A=32((x3)x2)dx,A = \int_{-3}^{2} \left( (x - 3) - x^2 \right) \, dx, where (x3)(x - 3) is the upper boundary and x2x^2 is the lower boundary.

  5. Evaluate the integral: A=32(x3x2)dx=32(x2+x3)dx.A = \int_{-3}^{2} (x - 3 - x^2) \, dx = \int_{-3}^{2} (-x^2 + x - 3) \, dx.

    Now, we compute the integral: (x2+x3)dx=x33+x223x.\int (-x^2 + x - 3) \, dx = -\frac{x^3}{3} + \frac{x^2}{2} - 3x. Evaluating from 3-3 to 22: [ A = \left[-\frac{(2)^3}{3} + \frac{(2)^2}{2} - 3(2)\right] - \left[-\frac{(-3)^3}{3} + \frac{(-3)^2}{2} - 3(-3)\right]. ]

    Calculating the values: [ = \left[-\frac{8}{3} + 2 - 6\right] - \left[\frac{27}{3} + \frac{9}{2} + 9\right]. ] [ = \left[-\frac{8}{3} - 4\right] - \left[9 + 4.5 + 9\right]. ] [ = \left[-\frac{8}{3} - \frac{12}{3}\right] - [22.5]. ] =20322.5=20367.53=87.53.= -\frac{20}{3} - 22.5 = -\frac{20}{3} - \frac{67.5}{3} = -\frac{87.5}{3}. Thus, the area AA is: A=87.53 square units.A = \frac{87.5}{3} \text{ square units}.

Summary

The area bounded by the curves is 87.53\frac{87.5}{3} square units.

Do you need any details or have questions? Here are some related questions for further exploration:

  1. How would the area change if the bounds were altered?
  2. What is the significance of the intersection points in determining the area?
  3. Can this method be applied to other bounded areas defined by different functions?
  4. How does changing the shape of the curves affect the integration process?
  5. What are alternative methods for calculating the area between curves?

Tip: Always sketch the curves to visualize the bounded area before setting up the integral.

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Math Problem Analysis

Mathematical Concepts

Calculus
Double Integrals
Area Between Curves

Formulas

A = ∫[a,b] (upper boundary - lower boundary) dx

Theorems

Fundamental Theorem of Calculus

Suitable Grade Level

Grades 11-12