Diff Equations: Theorem of Uniqueness

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SUMMARY

The discussion focuses on the uniqueness of solutions for the initial value problem defined by the differential equation y' = y^(1/2) with the initial condition y(4) = 0. The participant initially proposed y(t) = (t/2)^2, which leads to two solutions, thus violating the uniqueness condition. Clarification was provided that the function y(t) = (t/2)^2 is not valid at t = 4 due to non-differentiability, and the theorem of uniqueness applies since the function f = y^(1/2) and its partial derivative are continuous except where y ≤ 0, confirming that the uniqueness condition is satisfied in the defined rectangle R containing the point (4,0).

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Homework Statement



Check if the given initial value is a unique solution.

Homework Equations



y'=y^(1/2), y(4)=0

The Attempt at a Solution



I got y(t)=(t/2)^2 and 0 at t=4

So, we have two solutions to i.v.p.; therefore, it's not a unique solution.

Is it correct?
 
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I have no idea what you mean by "y(t)= (t/2)^2 and 0 at t= 4". If you mean "y(t)= (t/2)^2 if t is not 4, y(4)= 0", it is not a solution because it is not differentiable at t= 4. If you mean that y(t)= (t/2)^2 is one solution and y= 0 for all t is another solution, that is not correct because y(t)= (t/2)^2 give y(4)= 4, not 0. Please show exactly what the problem said and what you have tried to do.
 
I guess I needed to mention about theorem of uniqueness. f=y^(1/2) and its partial derivative 1/2(root of y) are continuous except where y<=0. We can take any rectangle R containing the initial value point (4,0). Then the hypothesis of theorem of uniqueness is satisfied. How about this way?
 

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