Răspuns:
5. A. 28:7=4, 35:7=5 ⇒ (28, 35)=7
B. 35:7=5, 40:7=5 rest 5 ⇒ (35, 40)≠7
6. A. 18:9=2, 32:9=3 rest 5. 45:9=5 ⇒ (18, 32, 45)≠9
B. 27:9=3, 45:9=5, 63:9=7 ⇒ (27, 45, 63)=9
7. a) D₂₄={1, 2, 3, 4, 6, 8, 12, 24}
D₄₀=(1, 2, 4, 5, 8, 10, 20, 40}
(24, 40)=8
b) D₃₅={1, 5, 7, 35}
D₄₂={1, 2, 3, 6, 7, 14, 21, 42}
(35, 42)=7
8. 36=2²·3², 54=2·3³ ⇒ (36, 54)=2·3²=18 = D
9. 45=3²·5, 60=3·4·5 ⇒ (45, 60)=15
54=2·3³, 72=2³·3² ⇒ (54, 72)=18
60=2²·3·5, 72=2³·3² ⇒ (60, 72)=12
80=2⁴·5, 32=2⁵ ⇒ (80, 32)=16
10. a) D₃₀={1, 2, 3, 5, 6, 10, 15, 30}
D₄₅=(1, 3, 5, 9, 15, 45}
D₇₀=(1, 2, 5, 7, 10, 14, 35, 70}
(30, 45, 70)=5
b) D₂₈={1, 2, 4, 7, 14, 28}
D₄₂={1, 2, 3, 6, 7, 14, 21, 42}
D₇₀=(1, 2, 5, 7, 10, 14, 35, 70}
(28, 42, 70)=14
11. 24=2³·3, 36=2²·3², 60=2²·3·5
(24, 36, 60)=2²·3=12 =B
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