Question: Plotting problem

I have the following problem : plotting with the squareroot function somehow stops showing the whole graph as soon as the range of the input allows values less than -10, I have attached two pictures that show the transition:

 

This is still fine:

 

But here is an example where the graph is cropped:

How can I change this to get the whole graph ? Thanks a lot for your help !!

 

 

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