When X> is 1, 1/x < 1, (1/x)-1<; 0，( 1/X)- 1 & lt； [1/X]>0, but [1/X] is not an integer, so it is not considered.
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When (1) is proved, (2) is easy to say, and (2) is equivalent to multiplying (1) by-1, and the sign of inequality is changed.
The function has an upper bound, that is, there is a number K 1, which makes the function f (x); =K2, the necessary and sufficient condition for a function to be bounded on x is that there is both an upper bound and a lower bound on x, where x is within the domain of the function. The boundedness of a function has little to do with the domain, but mainly depends on its value, which is also related to the corresponding laws.
I'm a senior in high school. I haven't seen you for a long time. I hope it can help my schoolmates.