《高中代数疑难解析》(河南教育出版社)在第27页中给出“判定函数是否存在反函数”的一种方法是:若给定函数y=f(x)是从定义域到值域的单调函数,则y=f(x)在其定义域上存在着函数;否则,y=f(x)在其定义城上不存在反函数”。《高中代数》(上海科技出版社)在第130页中也说:“只有当函数y=f(x)在整个定义域内是单调函数时,这 “High school algebra problem analysis” (Henan Education Press) on page 27 gives a method of “determining whether a function has an inverse function”: if a given function y = f(x) is from the definition domain to the value domain The monotonic function, then y = f (x) exists in the domain of its function; otherwise, y = f (x) in its definition of the city there is no inverse function. “” High school algebra “(Shanghai Science and Technology Press) Page 130 also says: ”Only if the function y=f(x) is a monotonic function in the entire domain, this