Đáp án:
Giải thích các bước giải:
2/6+2/12+2/20+2/30+2/42+2/56
= 4/12+2/12+2/20+2/30+2/42+2/56
= 1/2+2/20+2/30+2/42+2/56
= 10/20+2/20+2/30+2/42+2/56
= 3/5+2/30+2/42+2/56
= 18/30+2/30+2/42+2/56
= 2/3+2/42+2/56
= 28/42+2/42+2/56
= 5/7+2/56
= 40/56+2/56
= 6/8