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Let $P$ be a polynomial of degree $\geq 2.$ Consider the I.V.P. $$\frac{dy}{dx}=P(y),y(0)=1.$$ Now by Picard Uniqueness theorem the above I.V.P has unique solution in any BOUNDED interval of $\mathbb{R}$ containing $0$ as our $f(x,y)$ is Globally Lipschitz. But i want some example such that the above problem does't have unique solution(more than degree of $P$) on $\mathbb{R}.$ Please help. Thanks a lot.

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    Have you tried $y' = y^2$? – 2017-01-06
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    how it has more than one solution – 2017-01-06
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    its solution is given by $\frac{-1}{x+c}$ and apply I.C. – 2017-01-06
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    The solution on $(-\infty, 1)$ is $y = 1/(1 - x)$. On $(1, \infty)$ you can give $y$ the same rule or set $y = 0$. – 2017-01-06
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    OK can we have more than two solution? – 2017-01-06
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    I mean more than degree of $P.$ – 2017-01-06
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    what about $y' = y^2 + 1$? There should be infinitely many solutions :-) – 2017-01-06
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    But tan function is not defined on $\mathbb{R}$ – 2017-01-06
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    And even with $y' = y^2$ you have infinitely solutions, right? On $(1, \infty)$, you can set $y = 1/(x-c)$ for any $c \in \mathbf R$. – 2017-01-06
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    Do you means two way defined like in above solution? Please if possible solve little more... – 2017-01-06
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    Ok ok i got it .....thanks a lot....you can type it in solution section so that any one can get help.... – 2017-01-06
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    @AlexMacedo the de $y'=y^{2},y(0)=1$ has unique solution with max interval as either $(-\infty, 1)$ or $(1,\infty).$ – 2017-01-06

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A polynomial is decidedly not globally Lipschitz, it is continuously differentiable and thus locally Lipschitz, but that is all.

As a consequence, the relevant version of the existence and uniqueness theorem is that for any initial condition there exists a unique solution on a small time interval around the initial time. This germ of a solution can be extended to a maximal solution which is also unique on its domain. Note that the domain will in general depend on the initial point.

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    But my question is about example ... – 2017-01-06
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    The same applies there. You were given examples for dynamical blow-up, make it more flexible using $y'=c(y-a)^2$. Compare with $y'=c(y-a)(y-b)$, $a – 2017-01-06