Răspuns :
1. Doua numere naturale care au exact 6 divizori sunt 12(1,2,3,4,6,12) si 20(1,2,4,5,10,20)
1. 12={1,2,3,4,6,12} 20={1,2,4,5,10,20}
2.a = 9²⁰⁰² - 7²⁰⁰⁰
U9¹ = 9
U9² = 1
U9³= 9
----------
U9²⁰⁰² = 1
U7^1=7
U7²=9
U7³=3
U7^4=1
------
U7^2000=1
=) Ua=2=)U^0a[tex] \neq [/tex] divizibil cu 10
2.a = 9²⁰⁰² - 7²⁰⁰⁰
U9¹ = 9
U9² = 1
U9³= 9
----------
U9²⁰⁰² = 1
U7^1=7
U7²=9
U7³=3
U7^4=1
------
U7^2000=1
=) Ua=2=)U^0a[tex] \neq [/tex] divizibil cu 10