Undetermined Coefficients Calculator

Build accurate trials for common nonhomogeneous equations. Check roots, resonance, and forcing patterns with confidence. Export results, compare examples, and follow practical solving steps.

Calculator Inputs

Choose a supported forcing model, enter the differential equation coefficients, and estimate a particular solution using the undetermined coefficients method.

Equation coefficients
Forcing model

Example data table

Example Equation Forcing model Typical trial form
1y″ − 3y′ + 2y = 4e^xExponentialxAe^x because e^x resonates
2y″ + y = 5x − 2PolynomialAx + B
3y″ + 4y = 3sin(2x)Trigonometricx[A sin(2x) + B cos(2x)]
4y″ − 2y′ + y = e^x(3 + 2x)Exponential-polynomialx^2e^x(A + Bx)
5y″ + 2y′ + 5y = e^(−x)[2sin(2x)+5cos(2x)]Exponential-trigonometrice^(−x)[A sin(2x) + B cos(2x)]

Formula used

The method solves linear equations of the form ay″ + by′ + cy = f(x), where f(x) belongs to a supported forcing family.

First solve the characteristic equation ar² + br + c = 0 to get the complementary solution yc.

Next choose a trial particular form yp that matches the forcing model: polynomial, exponential, trigonometric, exponential-polynomial, or exponential-trigonometric.

If any trial term duplicates a complementary term, multiply the entire trial function by x or x² until linear independence is restored.

This calculator then estimates unknown coefficients by applying L[y] = ay″ + by′ + cy to each trial basis term and solving the resulting linear system.

How to use this calculator

  1. Enter the coefficients for y″, y′, and y.
  2. Select the forcing model that matches the right-hand side of your equation.
  3. Provide amplitudes, degrees, exponential rates, or angular frequencies as required.
  4. Press Calculate to generate the complementary solution, trial function, resonance note, and estimated particular solution.
  5. Review the coefficient table and sample verification table.
  6. Use the CSV button to export tables or the PDF button to print the full page.

Frequently asked questions

1. What does this calculator solve?

It handles second-order linear differential equations with constant coefficients and supported forcing terms suited to the undetermined coefficients method.

2. What forcing functions are supported?

It supports polynomial, exponential, sine-cosine, exponential-polynomial, and exponential-trigonometric inputs. These cover many textbook nonhomogeneous examples.

3. What is resonance here?

Resonance means a trial term already appears in the complementary solution. The calculator multiplies the trial by x or x² to restore independence.

4. Why are coefficients estimated numerically?

The tool builds and solves a linear system from the operator applied to each trial basis term. That gives reliable coefficients for supported models.

5. Can I use it for variable coefficients?

No. The method shown here is designed for constant-coefficient equations. Variable-coefficient problems usually need different techniques.

6. Why does the calculator sometimes show a singular system?

A singular system means the chosen data produced dependent trial equations or unstable matching points. Adjusting coefficients or forcing type usually resolves it.

7. Does the sample table prove the result exactly?

It provides a practical check at selected x values. It is a verification aid, not a formal symbolic proof.

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Important Note: All the Calculators listed in this site are for educational purpose only and we do not guarentee the accuracy of results. Please do consult with other sources as well.