Generally, the most common test method is to ask you the convergence and divergence of an integral, or to ask you to find a definite integral (this integral is a generalized integral). When x→a+, f(x) must be infinite. And the order of infinitesimal can not be higher than a certain scale to ensure convergence; This scale value is generally equal to 1. Pay attention to identify improper integral.

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The integral interval of definite integral is limited and the integrand function is bounded. However, in practical application and theoretical research, we will encounter some functions defined in infinite interval or unbounded functions in finite interval, and we also need to consider problems like definite integral. Therefore, it is necessary to generalize the concept of definite integral and make it applicable to the above two kinds of functions. This kind of generalized integral, because it is different from the usual definite integral, is called generalized integral, also called generalized integral. ?