=100 nha

dễ mà bạn, bạn chỉ cần bỏ ngoặc rồi cộng lại là được

1+3+5+7+9+11+13+15+17+19=100

=20x5=100

1+3+5+7+9+11+13+15+17+19

= (1+19)+(3+17)+(5+15)+(7+13)+(9+11)

= 20+20+20+20+20

= 20 x 5

= 100

(1+2+3+4+5+6+7+8+9+10+11+12+13+14+15+16+17+18+19+20 ) -1-5-9-3=

= ( 1 + 20 ) x 20 : 2 - 1 - 5 - 9 - 3 

= 210 - 1 - 5 - 9 - 3 

= 192

hok tốt

bn rảnh ghê ha

1+2+3+4+5+6+7+8+9+10+11+12+13+14+15+16+17+18+19+20-1-5-9-3=192

(8 x 7 - 16 - 5 x 8) x (1 + 2 + 3 + 4 + 5 + 6 + 7 + 8 + 9)

= [8 x 7 - 8 x 2 - 5 x 8] x [(1 + 9) + (2 + 8 ) + (3 + 7) + (4 + 6) + 5]

= [8 x (7 - 2 - 5)] x [10 + 10 + 10 + 10 + 10 + 5]

= (8 x 0) x 45

= 0

1 + 3 + 5 + 7 + 9 + 11 + 13 + 15 + 17 + 19

= (1 + 9) + (3 + 7) + (5 + 15) + (11 + 19) + (13 + 17)

= 10 + 10 + 20 + 30 + 30

= 100

1+2+...+9+11+18+19=(1+19)+(2+18)+...+(9+11)=20+20+...+20=20*9=180

=(1+19)+(2+18)+...+(9+11)=20+20+20+20+20+20+20+20+20=20x9=180

Số số hạng là :

19 - 1 + 1 = 19 ( số hạng )

Tổng trên là :

( 1 + 19 ) x 19 : 2 = 190

Vậy tổng trên là : 190

Click mik , mik click lại !!!!!!!!!!!!!!!!!!!!!!!!

Tổng hai số là : 

  (1+19)+(2+18)+(3+17)+(4+16)+(5+15)+(6+14)+(7+13)+(8+12)+(9+11)=180

         Đáp số : 180

=210 k nha

turbo pascal là ra ngay

1+2+3+4+5+6+7+8+9+10+11+12+13+14+15+16+17+18+19+20+21=231

trả lời:

=231

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= 1+(2-3)+(4-5)+(6-7)+........+(18-19)+20

= 1+(-1)+(-1)+(-1)+........+(-1)+20

= 1+(-9)+20

= 12

Tính: 1+2-3+4-5+6-7+8-9+10-11+12-13+14-15+16-17+18-19+20 = ?

= 1+(2-3)+(4-5)+(6-7)+........+(18-19)+20

= 1+(-1)+(-1)+(-1)+........+(-1)+20

= 1+(-9)+20

= 12

nhé !