Post

Created by @nathanedwards
 at October 31st 2023, 6:40:31 am.

Question:

Consider the differential equation dy/dx = x + 2.

  1. Compute the value of the derivative at x = 1.
  2. Sketch the slope field for the given differential equation on the interval -2 ≤ x ≤ 2 and -2 ≤ y ≤ 2.
  3. Using the slope field, estimate the solution to the differential equation that satisfies the initial condition y(0) = -1.
  4. Find the exact solution to the differential equation with the given initial condition.

Answer:

  1. To compute the value of the derivative at x = 1, substitute x = 1 into the differential equation dy/dx = x + 2:

    dy/dx = x + 2 dy/dx = 1 + 2 dy/dx = 3

    Therefore, the value of the derivative at x = 1 is 3.

  2. To sketch the slope field, we plot small line segments at various points on the x-y plane based on the slope at those points. The slope at each point (x, y) is given by x + 2.

    The following slope field is obtained:

    Slope Field

  3. To estimate the solution to the differential equation that satisfies the initial condition y(0) = -1, we use the slope field. Starting from the point (0, -1), we follow the slope field lines to sketch the approximate solution curve.

    Starting from (0, -1), at x = 0, the slope is 2. We move upward by 2 units to reach the next point. At x = 1, the slope is 3. We move upward by 3 units to reach the next point. Continuing this process, we sketch the approximate solution curve as follows:

    Approximate Solution

    Based on the slope field, the approximate solution to the differential equation that satisfies the initial condition y(0) = -1 is shown by the curve above.

  4. To find the exact solution to the differential equation with the given initial condition, we need to integrate both sides of the equation.

    dy/dx = x + 2

    ∫dy = ∫(x + 2)dx

    Integrating both sides, we get:

    y = (1/2)x^2 + 2x + C

    Now, using the initial condition y(0) = -1, we can solve for the constant C:

    -1 = (1/2)(0)^2 + 2(0) + C -1 = C

    Therefore, the exact solution to the differential equation with the initial condition y(0) = -1 is:

    y = (1/2)x^2 + 2x - 1