Because any real number X holds, its graph should be a parabola with an opening facing down, which is m-2.

So the range of m is -2.

6. The domain is to bring the value of x into X-2, that is,-1≤X-2≤2, and get 1≤X≤4.

I have no time to think about other topics now. I'll see them in the evening, haha. ...