Note the functions F1 (x) = f (x), F2 (x) = f (f (x)),... FN (x) = f (f... F (x)), and the intersection of the definition fields of these functions is d. if any x belongs to D Note that functions F1 (x) = f (x), F2 (x) = f (f (x)),... FN (x) = f (f... F (x)), the intersection of these function definition fields is d. if any x belongs to D, all n values satisfying FN (x) = f (x) constitute a set P, and all n values satisfying FN (x) = x constitute a set Q. (1). If f (x) = 1 / x, find sets P and Q, (2). For function f (x) = ax / (x + B) (a ＜ 0), 2 belongs to Q, find the relationship between a and B

Note the functions F1 (x) = f (x), F2 (x) = f (f (x)),... FN (x) = f (f... F (x)), and the intersection of the definition fields of these functions is d. if any x belongs to D Note that functions F1 (x) = f (x), F2 (x) = f (f (x)),... FN (x) = f (f... F (x)), the intersection of these function definition fields is d. if any x belongs to D, all n values satisfying FN (x) = f (x) constitute a set P, and all n values satisfying FN (x) = x constitute a set Q. (1). If f (x) = 1 / x, find sets P and Q, (2). For function f (x) = ax / (x + B) (a ＜ 0), 2 belongs to Q, find the relationship between a and B

（1）f[f(x)]=f(1/x)]=x.Q={y|y=2n,n∈N+}.f{f[f(x)]}=f(x).P={y|y=2n+1,n∈N+}.(2)2∈Q,∴f[f(x)]=f[ax/(x+b)]=[a*ax/(x+b)]/[ax/(x+b)+b]=a^2*x/[(a+b)x+b^2]=x,∴a+b=0.

Let the domain of function f (x) = LG (2x-3) be set M and the domain of function g (x) = √ (1-2 / x-1) be set n. find the intersection of sets m, N, m and n

The domain of F (x) is (3 / 2, + ∞) and the domain of G (x) is (- ∞, 1) ∪ [3, + ∞) ‡ m, and the intersection of n is [3. + ∞)

Given the function y = f (x), X ∈ [a, b], then the number of elements in the set {(x, y) | y = f (x), X ∈ [a, b]} ∩ {(x, y) | x = 2} is () A. 1 B. 0 C. 1 or 0 D. 1 or 2

From the perspective of function, the problem is to find the number of intersections between the image of function y = f (x), X ∈ [a, b] and line x = 2 (this is the transformation from one degree to shape),
Many students often mistakenly think that the intersection is one and say that it is obtained according to the "unique determination" in the function definition, which is incorrect,
Because the function is composed of three elements: definition domain, value domain and correspondence rule
It is given here that the domain of the function y = f (x) is [a, b], but the relationship between 1 and [a, b] is not clearly given. When 1 ∈ [a, b], there is an intersection, and when 1 ∈ [a, b], there is no intersection,
Therefore, C

Given the function y = f (x) (x ∈ [a, b]), then the set {(x, y) | y = f (x), X ∈ [a, b]} ∩ {(x, y) | x = C}, and the number of elements is

1 or 0 if C belongs to [a, b], then it is defined by the function: each element X in the definition field corresponds to the unique element f (x) in the value field. At this time, the intersection in the question has a point (C, f (c)). If C does not belong to [a, b], then {(x, y): the cross sitting of the element in y = f (x), X ∈ [a, b]}

If the function y = f (x) (m < = x < = n) is known, the number of elements in the set a intersection B = {(x, y) | y = f (x), m < = x < = n} intersection {(x, y) | x = 0} is (selection) A.0 B. 1 or 0 C.1 D. 1 or 2

C

Given that the function y = f (x), X belongs to [a, b], what is the number of elements contained in {(x, y) | y = f (x), X belongs to [a, b]} intersection {(x, y) | x = 2}?

{(x, y) | x = 2}, X is fixed as 2, and y has no limit, so the qualified point is the straight line parallel to the Y axis and passing through the (2,0) point. {(x, y) | y = f (x), X belongs to [a, b]}, and the definition field of F (x) is [a, b]. If 2B, that is, 2 is no longer in the definition field of F (x), then the curve f (x) has no intersection with the straight line, and the intersection space-time set of the two sets