integral integral |x-y|dydx where x is from 0 to 1 and y is from 0 to 1.

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I don't know how to deal with this question because there is an absolute value.

I tried to split the range x to ( 0 to y and y to 1), but fail to get the correct answer. = =

Can anyone help me?

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if you think my question typed is not clear, plz see the attached file.