Set a = 1, set B = 2. Do these two sets intersect? So what is the intersection of set C = 1,2, set D = 2,3? Is it 2 or 2 and an empty set?

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• 1. `(1) The intersection of sets a and B means___ Union means___ They are expressed as___ ? (2) Let set I be a complete set, and set a be a subset of it___ , expressed in descriptive form as___ ?
• 2. 11. For two given sets a and B, a and B belong to a and B___ The set of elements is called the intersection of a and B
• 3. Two sets explore how to find the intersection of different elements If a = {X / y = - X & sup2; + 2} B = {Y / y = x & sup2; - 1}, then a ∩ B=_______ The set of a and B is______ But the elements of the two sets are different, one is x and the other is y. I remember that the direct intersection is empty
• 4. Set a = {x | K faction + faction / 4 is less than or equal to x, less than or equal to K faction + faction / 2, K belongs to Z}, set B = {x | 6 + x-x ^ 2 is greater than or equal to 0}, find a intersection B (faction is the one equal to 3.1415926 Because of the mobile phone, I can't get a pie,
• 5. Given the set a = {X / 3 less than or equal to x greater than 7}, B = {X / 2 less than x less than 10}, C = {X / 2x less than a} if B is a subset of C, find the value range of a?
• 6. As shown in figure 1-5-1, the line y = KX + B (k)
• 7. It is known that the solution set of the inequality kx-2 ＞ 0 (K ≠ 0) about X is x ＜ - 3, then the intersection of the line y = - KX + 2 and the X axis is X______ ．
• 8. The proposition "inequality m ^ 2 - M < x ^ 2 + X + 1 holds" is true. The range of real number m is obtained Methods only know that the right side of the inequality is always greater than 0 (x + 1 / 2) ^ 2 + 3 / 4 is greater than 0, and then it won't work. What should I do?
• 9. Let P: inequality x ^ 2 = 1 > A have two propositions, the solution set of P: inequality x ^ 2 = 1 > A is R; Q: 7-3a > 1 X ^ 2 = the square of X
• 10. It is known that a is the first quadrant angle (360K < a < 360K + 90), so why is k divided into odd and even when finding out which quadrant angle A / 2 is And what quadrant angle is a / 3? K = 3k, k = 3K + 1, k = 3K + 2. Why
• 11. Let u = {x x = k, K ∈ Z}, q = x x = 2K, K ∈ Z}, t = {x x = 2K + 1, K ∈ Z} a. The complement of q = t b. Q ∪ t is the proper subset of U c. Q is the proper subset of T d. T is the true son of Q Which of them is right and why not B
• 12. It is known that the distance between points a (a, 2) and B (2, a + 1) is equal to the root sign 5, and the value of a is obtained
• 13. 2B = √ 245 - √ 3 - √ 147 - √ 5 2B = radical (radical 245 - radical 3) - radical (radical 147 - radical 5) Original title: Given a + B = radical (7 radical 5-radical 3), A-B = radical (7 radical 3-radical 5), find: ① AB, ② A & sup2; + B & sup2; And how to make a complete root with the computer Other people don't understand
• 14. Given a (2,5, - 1), B (5,1,11), find the direction cosine and direction angle of AB vector,
• 15. The vector a = (x, √ 3Y), B = (1,0), and (a + √ 3b) ⊥ (a - √ 3b) are known (1) Find the equation of LOCUS C of point m (x, y) satisfying the above conditions (2) Let the curve C and the straight line y = KX + m (K ≠ 0) intersect at two different points P, Q, and a (0, - 1). When | AP | = | AQ |, the value range of the real number m is obtained
• 16. The width of both the outer lane and the inner lane on the runway is 0.6 meters. In the 200 meter race, compared with the inner lane, how many meters should the starting point of the outer lane go forward?
• 17. Square of (a + b) + 6 (a + b) - 16, factorized
• 18. Please explain the definition of prime number and composite number for me
• 19. Finding prime numbers and composite numbers within 100 Write clearly
• 20. What are the factors of 42? In these numbers () is prime and () is composite