The eight functions of high school mathematics are: power function, exponential function, logarithmic function, inverse function, linear function, quadratic function, inverse proportional function and check function. Properties of function: Boundedness of folding function: Let the domain of function f(x) be D, and the number set X is contained in D. If the number K 1 exists, so that f(x)≤K 1 holds for any x∈X, then the function f(x) is said to have an upper bound on x, and k/0/ If there is a number K2 that makes f(x)≥K2 hold for any x∈X, the function f(x) has a lower bound on x, and K2 is a lower bound on x. If there is a positive number M that makes |f(x)|≤M hold for any x∈X, the function F is called. The necessary and sufficient condition for the function f(x) to be bounded on X is that it has both upper bound and lower bound monotonicity of folding function on X: Let the domain of function f(x) be D and the interval I be included in D ... If for any two points on the interval I, x 1 and x2, when X 1