Separable equations

Separable equations are a type of ordinary differential equation (ODE) that can be expressed in the form:

dydx=g(x)h(y)\frac{dy}{dx} = g(x) h(y)

In this form, the variables can be separated, meaning that all terms involving yy can be moved to one side of the equation and all terms involving xx to the other side. This allows for the equation to be rewritten as:

1h(y)dy=g(x)dx\frac{1}{h(y)} dy = g(x) dx

Once separated, both sides can be integrated independently. The solution process typically involves:

  1. Separating Variables: Rearranging the equation to isolate terms involving yy on one side and xx on the other.
  2. Integrating Both Sides: Performing the integration on both sides.
  3. Solving for yy: If possible, solving the resulting equation for yy.

Separable equations are particularly useful because they often have straightforward solutions and can be applied in various fields such as physics, biology, and engineering.

Part 1: Separable equations introduction

"Separation of variables" allows us to rewrite differential equations so we obtain an equality between two integrals we can evaluate. Separable equations are the class of differential equations that can be solved using this method.

Sure! Here are the key points to learn when studying "Separable Equations":

  1. Definition: A separable differential equation can be expressed in the form dydx=g(x)h(y)\frac{dy}{dx} = g(x)h(y), allowing the variables to be separated on each side of the equation.

  2. Separation of Variables: Rearrange the equation to isolate the variables:

    1h(y)dy=g(x)dx.\frac{1}{h(y)} dy = g(x) dx.
  3. Integration: Integrate both sides:

    1h(y)dy=g(x)dx.\int \frac{1}{h(y)} dy = \int g(x) dx.
  4. General Solutions: The result of integration will yield a general solution which may include an arbitrary constant CC.

  5. Finding Particular Solutions: If an initial condition is provided, substitute it into the general solution to find the particular constant.

  6. Checking Solutions: Always verify that any derived solution satisfies the original differential equation.

  7. Applications: Separable equations often model real-world phenomena, such as population dynamics and cooling laws.

  8. Limitations: Not all differential equations are separable; other techniques may be needed for non-separable equations.

By mastering these concepts, you'll have a solid foundation in solving separable differential equations.

Part 2: Addressing treating differentials algebraically

Addressing treating differentials algebraically

When studying "Addressing Treating Differentiate Algebraically," focus on these key points:

  1. Understanding Differentials: Grasp the concept of differentials and their role in calculus, particularly in relation to rates of change.

  2. Algebraic Techniques: Learn how to manipulate algebraic expressions to simplify or solve differential equations.

  3. Rules of Differentiation: Familiarize yourself with the basic rules of differentiation (product rule, quotient rule, chain rule) and how they apply to different types of functions.

  4. Implicit Differentiation: Understand how to differentiate equations that are not explicitly solved for one variable in terms of another.

  5. Higher-Order Derivatives: Study the concept of higher-order derivatives and their significance in analyzing function behavior.

  6. Applications: Explore real-world applications of differentiation in physics, engineering, and other fields.

  7. Common Mistakes: Be aware of common errors made in differentiation and algebraic manipulation to avoid them in practice.

  8. Practice Problems: Engage in solving a variety of problems to reinforce the concepts and techniques learned.

By mastering these points, you'll establish a solid foundation for addressing and treating differentials algebraically.

Part 3: Worked example: identifying separable equations

Separable equations can be written in the form dy/dx=f(x)g(y). See how we analyze various differential equations to see if they are separable.

When studying "Worked example: identifying separable equations," focus on the following key points:

  1. Definition of Separable Equations: Recognize that a differential equation is separable if it can be expressed in the form dydx=g(x)h(y)\frac{dy}{dx} = g(x)h(y).

  2. Rearranging the Equation: Learn how to rearrange the equation to isolate terms involving yy on one side and terms involving xx on the other side.

  3. Integrating Both Sides: Understand that once separated, both sides of the equation can be integrated independently to find the general solution.

  4. Constant of Integration: Remember to include a constant of integration during the integration process.

  5. Examples and Practice: Work through examples to solidify your understanding of identifying and solving separable equations.

  6. Recognizing Non-Separable Equations: Be able to identify equations that cannot be separated and explore alternative methods for solving them.

By mastering these points, you'll be well-equipped to handle separable equations in differential equations.

Part 4: Worked example: finding a specific solution to a separable equation

Solving a separable differential equation given initial conditions. In this video, the equation is dy/dx=2y² with y(1)=1.

When studying worked examples on finding a specific solution to separable equations, focus on these key points:

  1. Definition of Separable Equations: Recognize that a separable equation can be written in the form dydx=g(y)h(x)\frac{dy}{dx} = g(y)h(x), allowing separation of variables.

  2. Separation of Variables: Rearrange the equation to isolate yy and xx terms: 1g(y)dy=h(x)dx\frac{1}{g(y)} dy = h(x) dx.

  3. Integration: Integrate both sides independently:

    • The left side with respect to yy,
    • The right side with respect to xx.
  4. General Solution: After integration, combine results and add an arbitrary constant CC.

  5. Specific Solution: Use initial conditions or specific values given in the problem to solve for CC and obtain the particular solution.

  6. Verification: Check your derived solution by differentiating it to ensure it satisfies the original equation.

By concentrating on these steps, you will understand how to approach and solve separable differential equations effectively.

Part 5: Worked example: separable equation with an implicit solution

Sometimes the solution of a separable differential equation can't be written as an explicit function. This doesn't mean we can't use it!

When studying a worked example of a separable equation with an implicit solution, key points to focus on include:

  1. Understanding Separable Equations: Recognize that separable equations can be expressed in the form dydx=g(x)h(y)\frac{dy}{dx} = g(x) h(y), allowing variables to be separated.

  2. Separation of Variables: Rearrange the equation to separate the variables yy and xx on different sides, typically resulting in 1h(y)dy=g(x)dx\frac{1}{h(y)} dy = g(x) dx.

  3. Integration: Integrate both sides independently. This often yields an implicit solution because the function of yy is not explicitly solved for yy.

  4. Implicit Solution: Understand that the result of the integration provides an equation involving both xx and yy, representing the relationship between the two variables.

  5. Initial Conditions: If provided, apply initial conditions to find any constants introduced during integration.

  6. Graphical Interpretation: Recognize that the implicit solution can often be graphed to visualize the relationship between xx and yy without explicitly solving for one in terms of the other.

  7. Revisiting Solutions: Learn that, in some cases, implicit solutions can be solved for yy explicitly, but not always.

These key points provide a foundational understanding of solving and analyzing separable equations resulting in implicit solutions.

Part 6: Separable equations (old)

An old introduction video to separable differential equations.

When studying separable equations, focus on these key points:

  1. Definition: Recognize that a separable differential equation can be expressed in the form dydx=g(x)h(y)\frac{dy}{dx} = g(x)h(y).

  2. Separation of Variables: Learn how to manipulate the equation to isolate the variables:

    • Rearrange to get 1h(y)dy=g(x)dx\frac{1}{h(y)} dy = g(x) dx.
  3. Integration: Understand the process of integrating both sides:

    • Integrate 1h(y)dy\int \frac{1}{h(y)} dy and g(x)dx\int g(x) dx.
  4. Integration Constants: Incorporate the constant of integration on one side, usually after integrating the right side.

  5. Solving for yy: Familiarize yourself with solving the resulting equation for yy where possible.

  6. Implicit vs Explicit Solutions: Recognize that sometimes the solution may be implicit, and not always possible to express explicitly.

  7. Initial Conditions: Learn how to apply initial conditions if provided to find specific solutions.

  8. Check Your Solution: Understand how to differentiate your final solution to verify its correctness.

  9. Applications: Be aware of practical applications of separable equations in real-world problems, such as population dynamics and decay processes.

  10. Example Problems: Practice with various examples to solidify understanding and identify common pitfalls.

By focusing on these points, you'll develop a solid understanding of separable differential equations.

Part 7: Separable equations example (old)

An old worked example video of solving separable equations.

When studying "Separable equations," focus on these key points:

  1. Definition: Separable equations can be expressed in the form dydx=g(x)h(y)\frac{dy}{dx} = g(x)h(y), where variables can be separated.

  2. Separating Variables: Rearrange the equation to isolate terms involving yy on one side and xx on the other, leading to 1h(y)dy=g(x)dx\frac{1}{h(y)} dy = g(x) dx.

  3. Integration: Integrate both sides separately. This typically results in two integrals, one with respect to yy and one with respect to xx.

  4. Solving the Equation: After integration, solve for yy if possible. This may give an explicit or implicit solution.

  5. Initial Conditions: If provided, use initial conditions to find the particular solution by substituting values into the general solution.

  6. Verification: Always verify the solution by differentiating and checking if it satisfies the original equation.

These points provide a framework for understanding and solving separable differential equations.