My attempt so far
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I should get pretending that I don't know how to solve so apparantly somehow I should be able to paritally integrate in such a way that I get and so get rid of that integral.
Try to only integrate the first one , there is a trick : we don't need to integrate the second one , it will be deleted finally !!
Using integration by parts ,
we can see the second integral can be deleted but note that before writing this
we should add one more line , it is
so followed by