Chapter 5: Problem 51
Find the general solution of the differential equation. $$ \frac{d y}{d t}=t(1-t), t \geq 0 $$
Short Answer
Expert verified
The general solution is \( y(t) = \frac{t^2}{2} - \frac{t^3}{3} + C \).
Step by step solution
01
Recognize the Equation Type
Identify the given differential equation as a first-order ordinary differential equation (ODE). It is in the standard form \( \frac{d y}{d t} = f(t) \), where \( f(t) = t(1-t) \). This indicates that we can solve it using integration.
02
Separate Variables
Since the equation is already in the form \( \frac{d y}{d t} = f(t) \), it can be directly integrated with respect to \( t \). Thus, we will integrate both sides: \(\int d y = \int t(1-t) \, dt \).
03
Integrate the Right Side
Expand the function to integrate: \( t(1-t) = t - t^2 \). Now integrate term-by-term: \[ \int (t - t^2) \, dt = \int t \, dt - \int t^2 \, dt. \]
04
Solve the Integrals
Compute each integral separately: - \( \int t \, dt = \frac{t^2}{2} \) - \( \int t^2 \, dt = \frac{t^3}{3} \) Combine these results: \[ \int (t - t^2) \, dt = \frac{t^2}{2} - \frac{t^3}{3}. \]
05
Write the General Solution
Include the constant of integration \( C \) to express the general solution: \[ y(t) = \frac{t^2}{2} - \frac{t^3}{3} + C. \] This is the general solution to the differential equation.
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
First-order Differential Equations
Ordinary differential equations (ODEs) form the foundation for describing many natural phenomena in fields like physics and engineering. A first-order differential equation is arguably the simplest of these kinds of equations. It involves derivatives and functions of only one variable, typically written in the form:
\[ \frac{d y}{d t} = f(t, y) \]
\[ \frac{d y}{d t} = f(t, y) \]
- "\( y \)" is the dependent variable.
- "\( t \)" is the independent variable.
- "\( f(t, y) \)" is a function of the independent variable and possibly the function \( y \) itself.
Integration
Integration is a central operation when dealing with first-order ODEs. The process involves finding an antiderivative or integrating both sides of the equation to find the solution. Understanding the following points is key:
- The primary goal is to "reverse" differentiation, moving from a rate of change (a derivative) back to a function.
- In the context of differential equations, integrating provides us with a function \( y(t) \) that satisfies the relationship given by the derivative \( \frac{d y}{d t} \).
- \( \int t \, dt = \frac{t^2}{2} \)
- \( \int t^2 \, dt = \frac{t^3}{3} \)
General Solution
The outcome of solving a differential equation is often a 'general solution,' which captures all possible solutions using a constant of integration. This highlights:
- The general solution represents an infinite family of curves, depending on the constant of integration \( C \).
- Substituting different values for \( C \) results in different specific solutions of the differential equation.