Question

柔ʕ º ᴥ ºʔ

請問這題要怎麼算？
感謝🥺

58-1
k
18. (
D ) (5+1)(5²+1)(5¹ +1)=¯
k=? (A) (B) 2 (C) 3 (D)4
(2)

Answer 1

Mer

k(5+1)(5^2 +1)(5^4 +1)=5^8 -1
5^8 -1=(5^4 +1)(5^4 -1)=(5^4 +1)(5^2 +1)(5^2 -1)
=(5^4 +1)(5^2 +1)(5+1)(5-1)
故 k=5-1=4