Răspuns:
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22.
x + 5 ≤ 17
x ≤ 17 - 5
x ≤ 12
A = {0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12}
x = 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12
x + 3 = 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15
5 divide 5, 10, 15
B = {2, 7, 12}
A U B = {0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12}
A \ B = {0, 1, 3, 4, 5, 6, 8, 9, 10, 11}
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23. a.
1 + 2 + 3 + ... + 45 = 45*46/2 = 45*23 = 5*9*23
1 + 2 + 3 + ...+ 69 = 69*70/2 = 69*35 = 3*23*5*7
cmmdc = 5*23*3 = 345
cmmmc = 5*9*23*7 = 7245
b.
1 + 2 + 3 + ...+ 105 = 105*106/2 = 105*53 = 3*35*53 = 3*5*7*53
1 + 2 + 3 + ...+125 = 125*126/2 = 125*53 = 5^3*53
cmmdc = 5*53 = 265
cmmmc = 3*5^3*7*53 = 139125
