Răspuns:
Explicație pas cu pas:
5) -5 <= 2x -9 <= 5
4 <= 2x <= 14 |:2
2 <= x <= 7
A = [2, 7] interval
-14 < 3x -5 < 4
-9 < 3x < 9 |:3
-3 < x < 3
B = (-3, 3)
AUB = (-3, 7), A∩B = [2, 3)
6) 1/2*3 = 1/2 -1/3
1/3*4 = 1/3 -1/4
..........
1/29*30 = 1/29 -1/30
a = 1/2 -1/3 +1/3 -1/4 + 1/4 -1/5 +...+1/29 -1/30 =
1/2 -1/30 = (15 -1)/30 = 14/30 = 7/15
0,(3)= 1/3
1/3 < 7/15 < 1/2 sau
10 < 14 < 15 (num.comun =30)
