Question

Cho N= 5 + 5^2 + 5^3 + 5^4 +5^5 + 5^6 + 5^7 + 5^8 + 5^9 +5^10 .chứng tỏ N chia hết 6

Answer 1

N=(5+5^2)+5^2x(5+5^2)+5^4x(5+5^2)+5^6x(5+5^2)+5^8x(5+5^2)

N=30+5^2x30+5^4x30+5^6x30+5^8x30

N=(1+5^2+5^4+5^6+5^8)x30

Vì 30 chia hết cho 6 nên N chia hết cho 6.

Answer 2

N=(5+5^2)+5^2x(5+5^2)+5^4x(5+5^2)+5^6x(5+5^2)+5^8x(5+5^2)

N=30+5^2x30+5^4x30+5^6x30+5^8x30

N=(1+5^2+5^4+5^6+5^8)x30

Vì 30 chia hết cho 6 nên N chia hết cho 6.

Answer 3

(1+5^2+5^4+5^6+5^8).x 5+5^3+5^5+ ... 5^9