Math Problem Statement

Find a particular solution

y Subscript pyp

of the following equation. Primes denote the derivatives with respect to x.

y Superscript left parenthesis 5 right parenthesis Baseline plus 2 y Superscript left parenthesis 3 right parenthesis Baseline plus 2 y double prime equals 8 x squared minus 3

Solution

To find a particular solution (ypy_p) for the given equation:

y(5)+2y(3)+2y=8x23y^{(5)} + 2y^{(3)} + 2y'' = 8x^2 - 3

we will use the method of undetermined coefficients.

Step 1: Analyze the right-hand side

The non-homogeneous term on the right-hand side is 8x238x^2 - 3, which is a polynomial of degree 2. For polynomials, the assumed form of ypy_p is another polynomial of the same degree as the right-hand side. Hence, let:

yp=Ax2+Bx+Cy_p = Ax^2 + Bx + C

where AA, BB, and CC are constants to be determined.

Step 2: Compute derivatives of ypy_p

yp=2Ax+B,yp=2A,yp(3)=0,yp(5)=0y_p' = 2Ax + B, \quad y_p'' = 2A, \quad y_p^{(3)} = 0, \quad y_p^{(5)} = 0

Substitute these derivatives into the original equation.

Step 3: Substitute into the differential equation

Substituting into:

y(5)+2y(3)+2y=8x23,y^{(5)} + 2y^{(3)} + 2y'' = 8x^2 - 3,

we get:

0+2(0)+2(2A)=8x23.0 + 2(0) + 2(2A) = 8x^2 - 3.

Simplify:

4A=8x23.4A = 8x^2 - 3.

Clearly, this equation only matches the constant term (3-3) and the x2x^2-coefficient, which implies AA is determined solely by (8x^2 such easily matches observations for manually-testing simpler-layer scenarios for degree o

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Math Problem Analysis

Mathematical Concepts

Differential Equations
Method of Undetermined Coefficients
Polynomials

Formulas

Assumed particular solution: y_p = Ax^2 + Bx + C
Derivatives of polynomials: y_p' = 2Ax + B, y_p'' = 2A

Theorems

Method of Undetermined Coefficients

Suitable Grade Level

Undergraduate (Calculus/Differential Equations)