x²-2x-15

x²-2x-15

（x-5）（x+3）

3 (2x + 3) & #178; - 15 = 0 to find x value

3（2x+3）²-15=0
（2x+3）²=5
2X + 3 = + - radical 5
X = (- 3 + radical 5) / 2
X = (- 3-radical 5) / 2

Let a = {a + 1 |, 3,5}, B = {2A + 1, A2 + 2a, A2 + 2a-1}, when a ∩ B = {2,3}, find a ∪ B

From a ∩ B = {2,3}, we can get that 2 ∈ a, | a + 1 | = 2, a = 1 or a = - 3 When a = - 3, B = {- 5, 3, 2}, a = {2, 3, 5}, a ∩ B = {3, 2}, so a = - 3, a ∪ B = {- 5, 2, 3, 5} (8 points)

Let a = {a ^ 2,2a-1, - 4}, B = {a-5,1-a, 9} (1) if 9 belongs to (A and b), find the value of real number a (2) if {9} = A and B, find the value of indicator a

According to the fact that (1) a ^ 2 ≠ 2a-1, 2a-1 ≠ - 4, a ≠ 1, a ≠ - 3 / 2 are obtained
(2) A-5 ≠ 1-A, a-5 ≠ 9, 1-A ≠ 9, a ≠ 3, a ≠ 14, a ≠ - 8
Second, the feeling should be a to B, so (1) (2) satisfies the premise that a ^ 2 = 9 or 2a-1 = 9
A = ± 3, a = 5, respectively,
When a = 3, a-5 and 1-A in B are equal, so they are omitted,
When a = 5, 1-A in B = - 4, intersecting with - 4 in a, which is not the meaning of the problem, so - 3 should be taken