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Exercise 3

Avg difficulty 2.5

Consider the initial value problem y′=3y2/3y(0)=0.\begin{aligned} y' & = 3y^{2/3} \\ y(0) & = 0. \end{aligned}

  1. Show that the constant function, y(t)≡0y(t) \equiv 0, is a solution to the initial value problem.

  2. Show that y(t)={0,t≤t0(t−t0)3,t>t0y(t) = \begin{cases} 0, & t \leq t_0 \\ (t - t_0)^3, & t \gt t_0 \end{cases} is a solution for the initial value problem, where t0t_0 is any real number. Hence, there exists an infinite number of solutions to the initial value problem.

  3. Explain why this example does not contradict the Existence and Uniqueness Theorem.

Judson, The ODE Project, §1.6 Existence and Uniqueness of Solutions, Exercise 3

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Adapted from The ODE Project © 2019–2025 Thomas W. Judson. Licensed under CC BY 4.0. Source: The ODE Project. Imported at revision 7935458.