Question

So sánh:

C=1+2+2^2+2^3+2^4+2^5và D=2^6-1

Answer 1

C=1+2+2*2+2*3+2*4+2*5

=>2C=2+2*2+2*3+2*4+2*5+2*6

=>2C-C=(2+2*2+2*3+2*4+2*5+2*6)-(1+2+2*2+2*3+2*4+2*5)

=>C=2*6-1

Mà D=2*6-1

=>D=C

Answer 2

Tong sau co chia het cho 3 khong ?

A=2 + 2^2 + 2^3 + 2^4 + 2^5 + 2^6 + 2^7 + 2^8

Đung minh cho 1 k