I don’t think it is one of the 10 Commandments. But not doing the work is, to put it politely, less than intelligent. The work is there for learning, not pretending.
It is not stealing; nothing was taken. As to cheating, you are not cheating the teacher; you are cheating yourself.
You re tied up in knots about the “moral issue” and failing to see what is right in front of you - your learning. Since you are a student, you should be familiar with how to do research on line; I suspect you could find a tutorial of how to do the work if you actually applied yourself.
If tests/quizzes are going to determine your grade, then you will fail the part which this problem entails; and since the last time I took math, one problem builds on the one before it, you likely will not be able to answer anything which builds on the problem you are struggling with.
It doesn’t matter whether the teacher cares or doesn’t care if you copy the answer; if you don’t know how to do the work, then you need to learn how. You are not in school for the grades; you are there to learn. Quit whining and start finding a way to learn how to solve the problem. There are suggestions above - a website is offered; or you can contact the school administration.