a) S=(2+22)+22(2+22)+24(2+22)+.....+298(2+22)
S=(2+22)(1+22+24+....+298)
s=6(1+22+24+....+298)
Vi 6 chia het cho 3.Suyra S chia het cho 3
Moi cac ban xem tiep phan sau vao ngay mai
a. S=2+2^2+2^3+2^4+...+2^100
= 2.(1+2)+2^3.(1+2)+2^5.(1+2)+....+2^99(1+2)
=2.3+2^3.3+2^5.3+...+2^99.3
=3.(2+2^2+2^5+...+2^99)
=> 3 chia hết cho 3
b. S=2+2^2+2^3+2^4+...+2^100
= 2.(1+2+4+8)+2^5.(1+2+4+8)+2^9(1+2+4+8)+...+2^96.(1+2+4+8)
=2.15+2^5.15+2^9.15+...+2^96.15
=> S chia hết cho 15
a) S = ( 2 + 2^2 ) + ( 2^3 + 2^4 ) + ... + ( 2^99 + 2^100 )
S = 2(1 + 2 ) + 2^3(1 + 2 ) + ... + 2^99( 1 + 2 )
S = 2 . 3 + 2^3 . 3 + ... + 2^99 . 3
S = 3( 2 + 2^3 + 2^99 ) chia hết cho 3
ý b, c làm tương tự