§1. Functions

A Grade 9 topic in Algebra: “§1. Functions” (pp. 3–5, M. Imaliev, A. Asanov, K. Jusupov, S. Iskandarov). Definition 1: if to every value x of some set of numbers a rule (call it f) assigns a number y=f(x), then a function is said to be defined on that set. The variable x is called the independent variable, or the argument, and y the dependent variable. The set of values of x for which the rule f determines the number y=f(x) is called the domain of the function, and the set of values the function takes is called its range. Definition 2: the graph of a function is the set of points of the coordinate plane whose abscissas are equal to the values of the argument and whose ordinates are the corresponding values of the function. The lesson finds the domains of y=4x³+x+2, y=(x−2)/(x+4), y=√(2x−6), y=√((x+3)/(x−4)) and draws the graphs of y=√x, y=√(x−3)−4 and y=|x|.