<p>Your example could be a useful question for others at the same basic level&mdash;I'll bet some introductory texts don't explicitly point out that coefficients can be negative &amp; explain how to interpret them in that case (which is a further, implicit, question).</p>

<p>I can't see any reason to proscribe low-level/trivial questions, not least because we'd spend more time trying to define "low-level/trivial" (and arguing with askers who dispute the classification of their question as such) than we would answering them. That's not to say anything goes: "How do I calculate the geometric mean?" isn't a good question because we presume anyone who uses the term "geometric mean" has looked up how to calculate it &amp; has a particular difficulty in understanding the procedure that they're not telling us.</p>

<p>One might almost say that "low-level" can only apply to answers, not to questions. In particular, it's not unusual for solutions to an applied problem to vary greatly in their statistical sophistication; but even theoretical issues can be dealt with in more or less depth. It's perhaps only exercises, with a tightly prescribed scope, that can be classified relatively easily (&amp; that suggests a rationale for Math Overflow &amp; Mathematics SE).</p>
