chép thiếu đề rồi bạn \(S=1+2+2^2+2^3+...+2^7\)

\(=3+2^2\left(1+2\right)+2^4\left(1+2\right)+2^6\left(1+2\right)\)

\(=3\left(1+2^2+2^4+2^6\right)⋮3\)

=> S chia hết cho 3

     My village is about 10 kilometers (1) .............from............. Da Lat . It is a very beautiful  and (2).............peaceful............ place where people grow (3)...............flowers................ and vegetables only. It is very famous (4)............for........... its pretty roses and beautiful landscapes. The air is quite fresh, (5)...........however..........., the smell of the roses makes people fell cool. In spring, my village looks a (6).............carpet................ with plenty of colors. Tourists come to visit it so (7)..........often........... . Nowadays, with electricity , it doesn't take the villagers much time to (8).......water........ the roses . And even at night, people can walk along the (9)..........path......... and enjoy the (10)...........................fresh........................... smell of the flowers.

Complete the passage with the words given in the box .

from      often      carpet     path        howrver       peaceful       water        fresh          flowers       for

         My village is about 10 kilometers (1) ...........from............... Da Lat . It is a very beautiful  and (2)...........peaceful.............. place where people grow (3)..............flowers................. and vegetables only. It is very famous (4)............for........... its pretty roses and beautiful landscapes. The air is quite fresh; (5).........however............., the smell of yhe roses makes people fell cool. In spring, my village looks a (6).............carpet................ with plenty of colors. tourists come to visit it to (7)...........often.......... . Nowadays, with electricity , it doesn't take the villagers much time to (8)........water....... the roses .And even at night, people can walk along the (9)........path........... and enjoy the (10)............................fresh.......................... smell of the flowers.

\(2A=2^2+2^3+2^4+...+2^{2018}\)

\(A=2A-A=2^{2018}-2< B=2^{2018}\)

S = 1+2+2² + 2³ + 2⁴ + 2⁵ + 2⁶ + 2⁷ 

S = (1+2)+( 2² + 2³ ) + ( 2⁴ + 2⁵ ) + ( 2⁶ + 2⁷)

S = 3 +2²(1+2) + 2⁴(1+2) + 2⁶(1+2)

S = 3+ 2² .3 + 2⁴ .3 + 2⁶.3

S = 3(1+2² + 2⁴ + 2⁶) \(⋮\) 3

=> đpcm

khối lượng 2 gói kẹo+5g là:100+50+20+10=180g

khối lượng 2 gói kẹo là:180-5=175g

khối lượng 1 gói kẹo là:175:2=87,5g

hok tốt:))