Question

[trinh]

Tính tổng : A=38/25 + 9/10 - 11/15 + 13/21 - 15/28 + 17/36 - ................+197/4851-199/4950

Answer 1

[Ngô Trung Hiếu]

A= 38/25+9/10-11/15+13/21-15/28+17/36-...+197/4851-199/4950

Ta có thể viết lại : (9/20-11/15)+(13/21-15/28)+17/36-19/45...+(197/4851-199/4950)

Ta thấy:(9/10-11/15)=1/6=1/2x3=1/2-1/3

(13/21-15/28)=1/12=1/3x4=1/3-1/4

(17/36-19/45)=1/20=1/4x5=1/4-1/5

............................

Ta được:9/10-11/15+13/21-15/28+17/36-19/45...+197/4851-199/4950=1/2-1/3+1/3-1/4+1/4-1/5=24/50

Vậy:A= 38/25+24/50

A=2

Answer 2

[Ngô Trung Hiếu]

A=2 nhé bạn