Is the function integrable by Lebesgue on a ray

Hello! I was very tormented with this Lebesgue-related problem. I searched the whole Internet, but I didn't find a solution (maybe I was looking in the wrong places). The task looks like this:

Is the function integrable by Lebesgue on a ray (-∞,-1)?

if it is, then find its value.


I've tried to find Riemann improper integral

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But in the end, there happens division by zero (in first addendum)

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I'm not asking for a complete solution, but at least a hint in which direction to move, which theorems to use, otherwise I'm completely desperate. Thanks!



PS I'm sorry if there is some wrong terminology - I'm not native english speaker