Chapter 4: Problem 91
Solve the initial value problems in Exercises. $$\frac{d y}{d x}=2 x-7, \quad y(2)=0$$
Short Answer
Expert verified
The solution is \( y = x^2 - 7x + 10 \).
Step by step solution
01
Integrate the Differential Equation
We start by integrating the differential equation. The given equation is \( \frac{d y}{d x} = 2x - 7 \). To find \( y \), integrate with respect to \( x \): \( y = \int (2x - 7) \,dx = \int 2x\,dx - \int 7\,dx = x^2 - 7x + C \)Here, \( C \) is the integration constant.
02
Apply the Initial Condition
We use the given initial condition \( y(2) = 0 \) to find the constant \( C \). Substitute \( x = 2 \) and \( y = 0 \) into the integrated function: \( 0 = 2^2 - 7(2) + C \)\( 0 = 4 - 14 + C \)Solve for \( C \): \( C = 10 \)
03
Write the Particular Solution
Substitute the value of \( C \) back into the integrated function. The particular solution is:\( y = x^2 - 7x + 10\)
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Initial Value Problem
An Initial Value Problem (IVP) includes a differential equation along with specific values, known as initial conditions. These conditions define the value of the unknown function, usually at a certain point. In the problem exercise given, the differential equation \( \frac{dy}{dx} = 2x - 7 \) is accompanied by the initial condition \( y(2) = 0 \). This initial condition is essential because it allows us to determine a unique solution out of an infinite set of possible solutions. Without this condition, we would only have a general solution that includes an arbitrary constant.
- The differential equation indicates how \( y \) changes with \( x \).
- The initial condition pinpoints the specific path among all potential solutions by providing a concrete starting point.
Integration Process
The integration process is a crucial step in solving differential equations. It involves finding the integral of the equation, essentially reversing the process of differentiation. In our exercise, we start with the equation \( \frac{dy}{dx} = 2x - 7 \). To find \( y \), we integrate both sides of the differential equation with respect to \( x \). The process is broken down like this:
- Separate the terms: \( y = \int (2x - 7) \, dx \) becomes \( y = \int 2x \, dx - \int 7 \, dx \).
- Integrate each term separately: The integration of \( 2x \) with respect to \( x \) is \( x^2 \), and the integration of \( 7 \) is \( 7x \).
- The resulting general solution is: \( y = x^2 - 7x + C \), where \( C \) is the constant of integration.
Particular Solution
A particular solution of a differential equation is a solution that satisfies both the equation itself and any given initial conditions. In our problem, after integrating the differential equation into \( y = x^2 - 7x + C \), we need to find \( C \) using the initial condition \( y(2) = 0 \).Follow these steps to determine the particular solution:
- Plug in the initial condition values into the equation: \( 0 = 2^2 - 7(2) + C \).
- Solve the resulting equation: This gives us \( 0 = 4 - 14 + C \), which simplifies to \( C = 10 \).
- Substitute \( C \) back into the integrated equation to form the particular solution: \( y = x^2 - 7x + 10 \).