Exercise · ZW-WRONSKIAN-008 · ★★☆ Intermediate

Let \(y_1,y_2\) be solutions of \(y''+py'+qy=0\), with \(p,q\) continuous, and suppose \(W(y_1,y_2)(t_0)\neq0\) at a point \(t_0\). What follows?

Choose one option.

Show answer
  • A. They form a fundamental set: \(c_1y_1+c_2y_2\) gives every solution

Explanation

A nonzero Wronskian at a single point suffices: it lets you match any \(y(t_0)\) and \(y'(t_0)\), and by uniqueness you get every solution.

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Review the concept: Wronskian

The Wronskian \(W\) of two differentiable functions \(y_1\) and \(y_2\) is the determinant of the matrix formed by them and their first derivatives.

\[W(y_1,y_2)=\begin{vmatrix}y_1&y_2\\y_1'&y_2'\end{vmatrix}=y_1y_2'-y_1'y_2\]

More practice problems: wronskian

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