A= 3 +32 + 33 +34+...+3252 3 4 56 7 8 9 22 23 24 25+ + +++ + + +...

Bài 5

A= 3 +3

²

+ 3

³

+3

⁴

+...+3

²⁵

2

3

4

5

6

7

8

9

22

23

24

2

5

+

+ +

+

+

+ + + +

+

)

(3

+ + +

3

3

3

(3

3

3

3 ) ...

=3 (3

3

3

3 )

( ) ( ) ( )

0,25

2

2

3

6

2

3

22

2

3

= +

+ + +

+

+ + +

+ +

+ + +

3

3 1 3 3

3

... 3

1 3 3

3

3 3 1 3 3

( )

6

2

2

= +

+

... 3

3 40 3

3

=

Vậy A chia 4 dư 3