Problem:

Evaluate

Solution:

I have two ways here:

First Way: integrate x then calculate 1/(D-1) for the result (wich is x^2/2)

Second Way: evaluate 1/(D-1) for x then integrate the result

The problem here is that the two ways gives different results!

first way gives:

second way gives:

What's wrong?

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Anyone know a good site contains practice problems in inverse differential operator??