I. Assemble

If there are n(nEM) elements in set A, the number of all different subsets of set A is n, and the number of all non-empty proper subset is February-1.

Second, the letter emblem

1. Find the domain of the function.

(1) Given the analytical formula of a function, the basis for finding the domain of the function is the meaning of the basic algebraic formula, such as the denominator of a fraction is not equal to zero, the roots of even roots are non-numbers, the base of zero exponential power is not zero, the real number of logarithm is greater than zero and the base is positive, which is not equal to 1, and the definition of trigonometric function.

(2) Finding the domain of a function often boils down to solving a set of inequalities. Be careful when solving the inequality group, use the number axis when solving the intersection, and pay attention to whether you can take the endpoint value or reach the value.

2. Find the range of known functions (you can find the range of several special functions).

2. Monotonicity of functions

(1) Let x 1 and x [6]; & ltx then(x； )-(x)& lt； () A, with increasing function on it: f (x; )-f(x:)& gt； 0-f(x) is a decreasing function on [a, o]

3. The parity of the function

If f(x)= () exists in any domain, then f(x) is even; For any x in the definition domain, if f (an x)=-f(x), then f(x) is odd function. Odd function's image is symmetrical about the origin, and even function's image is symmetrical about y.

4. Periodic function

For the number f6), if there is a non-zero constant t, so that when every value in the field is defined by X, there is fx+T)=fx), then the function fx) is called the period number, and the constant age t must be called the period of this number.

(2) Minimum positive period

If there is a minimum positive number in all cycles of a cycle, then this minimum orthodoxy is called the minimum positive cycle of fa.