研究函数的定义域、最值、单调性、周期性等问题,这对于给出了解析表达式的函数来讲,已是我们比较熟悉的一类数学问题,不过,研究函数的上述问题,并不一定要知道函数的解析表达式。特别是在函数的解析表达式由题设求不出,它仅用符号f(x)表示时,我们仍可以利用该函数的某些已知性质来研究该函数的上述问题。这类数学问 Studying the domain, maximum value, monotonicity, periodicity, etc. of the function, which is a class of mathematical problems that we are more familiar with given the analytical expressions of the function, however, we study the above problems of the function and It is not necessary to know the analytical expression of the function. In particular, when the analytical expression of a function cannot be solved by the problem and it is only represented by the symbol f(x), we can still use the known properties of the function to study the above problem of the function. This type of mathematics