Question

_{cmr : 2²+2³ ...2⁶⁰ chia hết cho 3 ;7}

Answer 1

Sửa đề: A=2+2^2+...+2^60

A=2(1+2)+...+2^59(1+2)

=3(2+...+2^59) chia hết cho 3

A=2(1+2+2^2)+...+2^58(1+2+2^2)

=7(2+...+2^58) chia hết cho 7