This is not restricted to integrals. If question B is equivalent to question A via a very simple argument (for example, a straight forward substitution in case of integrals), then question B should be closed as a duplicate of question A and one of the close voters should explain this simple argument in the comments.

The problem here is that "simple" is very subjective. What is simple and takes like 5 seconds of thought for an experienced mathematician can take a week for a less experienced student. So be careful. Some users have taken this too far in the past and close everything as a duplicate even if the argument that it's a duplicate requires a considerable effort (for the OP) and many steps (1, 2, 3). This is not OK in my opinion.

To prevent that a question gets closed without the OP getting the answer they need, you can do the following:

• Explain in a comment that question B is a duplicate of A because of [simple argument].
• Wait for feedback by the OP if they understand [simple argument].
• If yes, cast a close vote.
• If not, elaborate the [simple argument] in an answer. (Do not explain the simple argument more in the comments. This is not what comments are for.)

This is not restricted to integrals. If question B is equivalent to question A via a very simple argument (for example, a straight forward substitution in case of integrals), then question B should be closed as a duplicate of question A, and one of the close voters should explain this simple argument in the comments.

The problem here is that "simple" is very subjective. What is simple and takes like 5 seconds of thought for an experienced mathematician can take a week for a less experienced student. So be careful. Some users are taking this too far and close everything as a duplicate even if the argument that it's a duplicate requires a considerable effort (for the OP) and many steps (1, 2, 3). This is not OK in my opinion.

To prevent that a question gets closed without the OP getting the answer they need, you can do the following:

• Explain in a comment that question B is a duplicate of A because of [simple argument].
• Wait for feedback by the OP if they understand [simple argument].
• If yes, cast a close vote.
• If not, elaborate the [simple argument] in an answer. (Please do not explain the simple argument further in the comments, do that in an answer.)

This is not restricted to integrals. If question B is equivalent to question A via a very simple* argument, then question B should be closed as a duplicate of question A and one of the close voters should explain this simple argument in the comments.

*The problem here is that "simple" is very subjective. What is simple and takes like 5 seconds of thought for an experienced mathematician can take a week for a less experienced student. So be careful. Some users have taken this too far in the past and close everything as a duplicate even if the argument that it's a duplicate requires a considerable effort and many steps. This is not OK.

To prevent that a question gets closed without the OP getting the answer they need, you can do the following:

• Explain in a comment that question B is a duplicate of A because of [simple argument].
• Wait for feedback by the OP if they understand [simple argument].
• If yes, cast a close vote.
• If not, elaborate the [simple argument] in an answer.

This is not restricted to integrals. If question B is equivalent to question A via a very simple argument (for example, a straight forward substitution in case of integrals), then question B should be closed as a duplicate of question A and one of the close voters should explain this simple argument in the comments.

The problem here is that "simple" is very subjective. What is simple and takes like 5 seconds of thought for an experienced mathematician can take a week for a less experienced student. So be careful. Some users have taken this too far in the past and close everything as a duplicate even if the argument that it's a duplicate requires a considerable effort (for the OP) and many steps (1, 2, 3). This is not OK in my opinion.

To prevent that a question gets closed without the OP getting the answer they need, you can do the following:

• Explain in a comment that question B is a duplicate of A because of [simple argument].
• Wait for feedback by the OP if they understand [simple argument].
• If yes, cast a close vote.
• If not, elaborate the [simple argument] in an answer. (Do not explain the simple argument more in the comments. This is not what comments are for.)