128 VẬY S = 128127 - 21 = 127128−64 = 12863 .1 = 21 ; 1 =...

1 . - DE THI VA DAP AN HSG MON TOAN 5
DE THI VA DAP AN HSG MON TOAN 5

1

.

128

Vậy S =

128

127

-

2

1

=

127

128

−

64

=

128

63

.

1

= 2

1

;

1

= 2 x

1

= 2 x Cách 7. Ta có:

4

1

= 2 x

64

32

8

16

x

128

1

;

128

1

= 1 x

128

1

.Vậy S = 1 x

128

1

+ 2 x

128

1

+ 4 x

128

1

+ 8 x

128

1

+ 16 x

1

+ 32 x

1

= (32 + 16 + 8 + 4 + 2 + 1) x

1

= 63 x

1

=