Đáp án:
A=2020/1011
Giải thích các bước giải:
2/1x2+2/2x3+2/3x4+2/4x5+........+2/1010x1011
=2x(1/1x2+1/2x3+1/3x4+1/4x5+....1/1010x1011)
=2x(1/1-1/2+1/2-1/3+1/3-1/4+1/4-1/5+...+1/1010-1/1011)
=2x(1/1-1/1011)
=2x(1011/1011-1/1011)
=2x1010/1011
=2020/1011