non-linear differential equation
(noun)
nonlinear partial differential equation is partial differential equation with nonlinear terms
Examples of non-linear differential equation in the following topics:
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Separable Equations
- Separable differential equations are equations wherein the variables can be separated.
- Non-linear differential equations come in many forms.
- A separable equation is a differential equation of the following form:
- The original equation is separable if this differential equation can be expressed as:
- A wave function which satisfies the non-relativistic Schrödinger equation with $V=0$.
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Predator-Prey Systems
- The relationship between predators and their prey can be modeled by a set of differential equations.
- The predator–prey equations are a pair of first-order, non-linear, differential equations frequently used to describe the dynamics of biological systems in which two species interact, one a predator and one its prey.
- As differential equations are used, the solution is deterministic and continuous.
- However, a linearization of the equations yields a solution similar to simple harmonic motion with the population of predators following that of prey by 90 degrees.
- The solutions to the equations are periodic.
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Logistic Equations and Population Grown
- A logistic equation is a differential equation which can be used to model population growth.
- The logistic function is the solution of the following simple first-order non-linear differential equation:
- The equation describes the self-limiting growth of a biological population.
- Letting $P$ represent population size ($N$ is often used instead in ecology) and $t$ represent time, this model is formalized by the following differential equation:
- In the equation, the early, unimpeded growth rate is modeled by the first term $rP$.
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Nonhomogeneous Linear Equations
- In the previous atom, we learned that a second-order linear differential equation has the form:
- When $f(t)=0$, the equations are called homogeneous second-order linear differential equations.
- Linear differential equations are differential equations that have solutions which can be added together to form other solutions.
- Phenomena such as heat transfer can be described using nonhomogeneous second-order linear differential equations.
- Identify when a second-order linear differential equation can be solved analytically
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Linear Equations
- A linear equation is an algebraic equation in which each term is either a constant or the product of a constant and a single variable.
- A common form of a linear equation in the two variables $x$ and $y$ is:
- The parametric form of a linear equation involves two simultaneous equations in terms of a variable parameter $t$, with the following values:
- Linear differential equations are differential equations that have solutions which can be added together to form other solutions.
- Linear differential equations are of the form:
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Second-Order Linear Equations
- A second-order linear differential equation has the form $\frac{d^2 y}{dt^2} + A_1(t)\frac{dy}{dt} + A_2(t)y = f(t)$, where $A_1(t)$, $A_2(t)$, and $f(t)$ are continuous functions.
- Linear differential equations are of the form $Ly = f$, where the differential operator $L$ is a linear operator, $y$ is the unknown function (such as a function of time $y(t)$), and the right hand side $f$ is a given function of the same nature as $y$ (called the source term).
- where $D$ is the differential operator $\frac{d}{dt}$ (i.e.
- When $f(t)=0$, the equations are called homogeneous second-order linear differential equations.
- A simple pendulum, under the conditions of no damping and small amplitude, is described by a equation of motion which is a second-order linear differential equation.
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Linear Approximation
- A linear approximation is an approximation of a general function using a linear function.
- Linear approximations are widely used to solve (or approximate solutions to) equations.
- Given a twice continuously differentiable function $f$ of one real variable, Taylor's theorem states that:
- Therefore, the expression on the right-hand side is just the equation for the tangent line to the graph of $f$ at $(a, f(a))$.
- Since the line tangent to the graph is given by the derivative, differentiation is useful for finding the linear approximation.
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Linear Equations in Standard Form
- A linear equation written in standard form makes it easy to calculate the zero, or $x$-intercept, of the equation.
- Standard form is another way of arranging a linear equation.
- In the standard form, a linear equation is written as:
- However, the zero of the equation is not immediately obvious when the linear equation is in this form.
- Convert linear equations to standard form and explain why it is useful to do so
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Applications of Second-Order Differential Equations
- A second-order linear differential equation can be commonly found in physics, economics, and engineering.
- Examples of homogeneous or nonhomogeneous second-order linear differential equation can be found in many different disciplines, such as physics, economics, and engineering.
- The equation of motion is given as:
- Therefore, we end up with a homogeneous second-order linear differential equation:
- Identify problems that require solution of nonhomogeneous and homogeneous second-order linear differential equations
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The Equation of a Line
- In statistics, simple linear regression is the least squares estimator of a linear regression model with a single explanatory variable.
- This is because models which depend linearly on their unknown parameters are easier to fit than models which are non-linearly related to their parameters and because the statistical properties of the resulting estimators are easier to determine.
- A common form of a linear equation in the two variables $x$ and $y$ is:
- The origin of the name "linear" comes from the fact that the set of solutions of such an equation forms a straight line in the plane.
- In this particular equation, the constant $m$ determines the slope or gradient of that line, and the constant term $b$ determines the point at which the line crosses the $y$-axis, otherwise known as the $y$-intercept.