# When is an ode exact?

Last Update: April 20, 2022

This is a question our experts keep getting from time to time. Now, we have got the complete detailed explanation and answer for everyone, who is interested!

**Asked by: Miss Delores Powlowski**

Score: 4.2/5 (36 votes)

A first-order differential equation (of one variable) is called exact, or an exact differential, if it is the result of a simple differentiation. The equation **P(x, y)y′ + Q(x, y) = 0**, or in the equivalent alternate notation P(x, y)dy + Q(x, y)dx = 0, is exact if P_{x}(x, y) = Q_{y}(x, y).

## Which of the following is an exact ode?

Some of the examples of the exact differential equations are as follows : ( **2xy – 3x**^{2} ) dx + ( x^{2} – 2y ) dy = 0. ( xy^{2} + x ) dx + yx^{2} dy = 0. Cos y dx + ( y^{2} – x sin y ) dy = 0.

## Can a differential equation be linear and exact?

Linear & Exact Equations : Example Question #5

No. The equation does not take the proper form. Explanation: For **a differential equation to be exact, two things must be true**.

## Are exact equations separable?

A first-order differential equation is exact if it has a conserved quantity. For example, **separable equations are always exact**, since by definition they are of the form: M(y)y + N(t)=0, ... so ϕ(t, y) = A(y) + B(t) is a conserved quantity.

## How do you tell if an equation is separable or linear?

Linear: No products or powers of things containing y. For instance y′2 is right out. Separable: The equation can be put in the form dy(expression containing ys, but no xs, in some combination you can integrate)**=dx**(expression containing xs, but no ys, in some combination you can integrate).

## Exact Differential Equations

**35 related questions found**

### What is exact solution numerical analysis?

In mathematics, some problems can be solved analytically and numerically. An analytical solution involves framing the problem in a well-understood form and calculating the exact solution. A numerical solution means **making guesses at the solution and testing whether the problem is solved well enough to stop**.

### What is an exact solution?

As used in physics, the term "exact" generally refers to **a solution that captures the entire physics and mathematics of a problem** as opposed to one that is approximate, perturbative, etc. Exact solutions therefore need not be closed-form.

### Are Bernoulli equations linear?

This is a non-linear differential equation that can be reduced to a linear one by a clever substitution. ... The Bernoulli equation was one of the first differential equations to be solved, and is still one of very few non-linear differential equations that can be solved explicitly.

### Is algebra a linear equation?

A linear expression is **an algebraic expression** where each term is either a numeric constant or a variable raised only to the first power. It is most commonly seen in linear equations. Remember that just as in linear equations, coefficients can be either positive numbers or negative numbers.

### How do you solve an integrating factor?

We can solve these differential equations using the technique of an integrating factor. We multiply both sides of the differential equation by the integrating factor I which is defined as **I = e∫ P dx.** ⇔ Iy = ∫ IQ dx since d dx (Iy) = I dy dx + IPy by the product rule.

### What is the Y in Bernoulli's equation?

**y = 1x ^{2} (cos(x)+C)**

The Bernoulli Equation is attributed to Jacob Bernoulli (1655−1705), one of a family of famous Swiss mathematicians.

### What is Bernoulli's method?

A Bernoulli differential equation is **an equation of the form y′+a(x)y=g(x)yν**, where a(x) are g(x) are given functions, and the constant ν is assumed to be any real number other than 0 or 1. Bernoulli equations have no singular solutions.

### Why is Bernoulli's equation used?

Bernoulli's principle **relates the pressure of a fluid to its elevation and its speed**. Bernoulli's equation can be used to approximate these parameters in water, air or any fluid that has very low viscosity.

### What is the difference between exact and inexact differentials?

An exact differential such as means that there exists a state function such that its differential is . An inexact differential such as and , does not hold this property. ... In the case of mechanical work, for instance, **d W = p d V** where is the pressure and is the differential of the volume .

### Why is exact solution important?

It is significant that many equations of physics, chemistry, and biology contain empirical parameters or empirical functions. Exact solutions **allow researchers to design and run experiments**, by creating appropriate natural (initial and boundary) conditions, to determine these parameters or functions.

### Why are exact differential equations called exact?

Higher-order equations are also called exact **if they are the result of differentiating a lower-order equation**. ... If the equation is not exact, there may be a function z(x), also called an integrating factor, such that when the equation is multiplied by the function z it becomes exact.

### What is the formula of Newton Raphson method?

Therefore it has the equation **y = f ′ ( x n ) ( x − x n ) + f ( x n ) y = f'(x_n)(x - x_n) + f(x_n) y=f′(xn)(x−xn)+f(xn)**.

### What are the types of numerical methods?

**Types of Numerical Methods**

- Taylor Series method.
- Euler method.
- Runge Kutta methods (RK-2 and RK-4)
- Shooting method.
- Finite difference methods.

### Who is the father of numerical analysis?

Following **Newton**, many of the mathematical giants of the 18th and 19th centuries made major contributions to numerical analysis. Foremost among these were the Swiss Leonhard Euler (1707–1783), the French Joseph-Louis Lagrange (1736–1813), and the German Carl Friedrich Gauss (1777–1855).

### Can an ode be separable but not exact?

Separable first-order ODEs are ALWAYS exact. But **many exact ODEs are NOT separable**.

### Is dy dx e x/y separable?

So something like **dy/dx = x + y is not separable**, but dy/dx = y + xy is separable, because we can factor the y out of the terms on the right-hand side, then divide both sides by y.

### How Euler's method works?

Methodology. Euler's method uses the simple formula, **to construct the tangent at the point x and obtain the value of y(x+h)** , whose slope is, In Euler's method, you can approximate the curve of the solution by the tangent in each interval (that is, by a sequence of short line segments), at steps of h .

### Is Bernoulli equation exact?

Bernoulli equations are special because they are **nonlinear differential equations with known exact solutions**. A notable special case of the Bernoulli equation is the logistic differential equation.