Question

Giải giùm mình nha!

A=1/30+1/42+1/56+1/72+1/90+1/110+1/132

Answer 1

1/20 + 1/30 + 1/42 + ... + 1/156

= 1/4.5 + 1/5.6 + 1/6.7 + .... + 1/12.13

= 1/4 - 1/5 + 1/5 - 1/6 + 1/6 - 1/7 + ... + 1/12 - 1/13

= 1/4 - 1/13

= 9/52

Answer 2

1/20 + 1/30 + 1/42 + ... + 1/156

= 1/4.5 + 1/5.6 + 1/6.7 + .... + 1/12.13

= 1/4 - 1/5 + 1/5 - 1/6 + 1/6 - 1/7 + ... + 1/12 - 1/13

= 1/4 - 1/13

= 9/52

Answer 3

A=1/5.6+1/6.7+1/7.8+1/8.9+1/9.10+1/10.11+1/11.12

A=1/5-1/12
Tự tính

Answer 4

A= 1/30 + 1/42 + 1/56 + 1/72 + 1/90 +1/110 + 1/132

A= 1/5.6 + 1/6.7 + 1/7.8 + 1/8.9 + 1/9.10 + 1/10.11 + 1/11.12

A=1/5-1/6+1/6-1/7+1/7-1/8+1/8-1/9+1/9-1/10+1/10-1/11+1/11-1/12

A=1/5-1/12

A=12/6-5/60

A=7/60