Question

cho 2^n+1 là số nguyên tố (n>2). Chứng minh 2^n -1 là hợp số 

Answer 1

2ⁿ>2²=4>3 (vì n>2)

=>2ⁿ=3k+1;3k+2

xét 2ⁿ=3k+2 =>2ⁿ+1=3k+3=3(k+1) chia hết cho 3

=>2ⁿ+1 là hợp số (trái giả thuyết)

=>2ⁿ=3k+1

=>2ⁿ-1=3k+1-1=3k chia hết cho 3

=>2ⁿ-1 là hợp số

=>đpcm

Answer 2

sai rùi bạn ơi

Answer 3

sai rui

Answer 4

sai roiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiii