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The method of undetermined coefficients for PI: if f(x) = xe2x, the trial PI is:

Answer: (Ax + B)e2x.

  • A Axe2x
  • B (Ax + B)e2x
  • C Ae2x
  • D (Ax² + Bx)e2x

Correct answer: B. (Ax + B)e2x

Explanation: Rule: for f(x)=pₙ(x)eᵃˣ where pₙ is degree-n polynomial, trial PI=(Ax+B)e2x (same degree polynomial times e2x), provided 2 is not a root of the characteristic equation. Substitute into DE to find A and B.

Family of Solution Curves: y = Ax²Each value of the constant A gives ONE particular curve from the family

The general solution y=Ax² represents an entire FAMILY of curves, one for each value of the arbitrary constant A; a particular solution (fixed by an initial condition) selects exactly one curve from this family.

Concept context

Equations involving derivatives and their solutions

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