How many subsets of set {1,2,3. N}, and how many subsets only contain five elements? Just answer the back empty

The nth power NC5 of 2

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1. If the set has 39 elements, then there are several non empty proper subsets. Remember that there is a formula, what is it?
2. Write all subsets and proper subsets of set {a, B, C} Let's finish the problem by 22:00 this evening
3. If there are n elements in set a, then set a has n elements______ Subset, yes______ A true subset, yes______ A nonempty proper subset
4. The reason for the formula of the number of subsets of a finite set
5. What is the formula for subsets of numbers and non empty proper subsets,
6. Is an empty set a proper subset of all sets? Why? Some people say "non empty sets.",
7. An empty set is a proper subset of any set______ ．
8. What does it mean that an empty set is the only proper subset of a set? Make it clear. Take an example
9. If a subset of a contains n elements, how many subsets of a? How many nonempty subsets of a? How many nonempty proper subsets of a?
10. There are 2 ^ n subsets, 2 ^ n-1 nonempty subsets and 2 ^ n-2 nonempty proper subsets of set a with n elements What if n = 0
11. Find the set {1,2,3 n} The sum of the elements of all subsets of
12. Senior one mathematics compulsory 5, find the general formula In the sequence {an}, if A1 = 1 and an + 1 = 2An + 3, then the general term an of the sequence= Ask the master to give the answer, and give the steps!
13. Senior one mathematics compulsory five - find the general formula of the sequence! (1) 7,77,777,7777,. Find the general term formula of this sequence~ (2) The known sequence {an} is the arithmetic sequence, A1 = f (x + 1), A2 = 0, A3 = f (x-1), where f (x) = x ^ 2-4x + 2, find the general term formula It's mainly the first question! It doesn't matter if you can't work out the second one~
14. What I want is compulsory 3 knowledge points with examples
15. Fundamental theorem of plane vector If the point D is on the edge BC of the triangle ABC, and the vector CD = 4, the vector DB = m, the vector AB + N, the value of 3M + n Urgent..... Urgent..... Urgent..... Urgent..... Urgent..... Urgent..... Urgent..... Urgent..... Urgent..... Urgent..... Urgent..... Urgent..... Urgent..... Urgent..... Urgent
16. In △ ABC, B = 60 ° and B2 = AC, then the shape of △ ABC is_______ ．
17. If a line is parallel to a plane, is it parallel to all the lines in the plane or any line? What is "all" or "any"
18. Taking the vertex of the quadrilateral ABCD as a (m, n) B (6,1) C (3,3) d (2,5), the values of M and N are obtained, so that the quadrilateral ABCD is a right angle trapezoid
19. Exercise 3.3 on page 110, the first question of the last question in group B I have worked out is (4), the title is that the vertex a (5,1) of △ ABC is known, the equation of the line where the central line cm on the edge of AB is 2x-y-5 = 0, and the equation of the line where the high BH on the edge of AC is x-2y-5 = 0 (1) The coordinates of vertex C; (2) The equation of the straight line BC
20. It's depressing that I didn't bring the book with me Not too much. It's better to write down one point at the end of each summary on no more than one piece of paper Three lines per chapter... No books on holiday