Đáp án:
4, 100/101
5, 100/101
6, 50/101
7,350/101
Giải thích các bước giải:
4, 1/2+ 1/6+...+ 1/10100
= 1/1.2+ 1/2.3+....+ 1/100.101
= 1- 1/2+ 1/2- 1/3+....+ 1/100- 1/101
= 1- 1/101
= 100/101
5, A= 2/1.3+ 2/3.5+...+ 2/99.101
= 1- 1/3+ 1/3- 1/5+...+ 1/99- 1/101
= 1- 1/101
= 100/101
Vậy A= 100/101
6, A= 1/1.3+ 1/3.5+...+ 1/99.101
2.A= 2.( 1/1.3+ 1/3.5+...+ 1/99. 101)
2.A= 2/1.3+ 2/3.5+...+ 2/99.101
2.A= 1- 1/3+ 1/3- 1/5+...+ 1/99- 1/101
2.A= 1- 1/101
2.A = 100/101
A= 100/101: 2
= 50/101
7, A= 7/1.3+ 7/3.5+...+ 7/99.101
A= 7.( 1/1.3+ 1/3.5+....+ 1/99. 101)
2.A= 7.2.( 1/1.3+ 1/3.5+....+ 1/99.101)
2.A= 7.( 2/1.3+ 2/3.5+...+ 2/99.101)
2.A= 7.( 1- 1/3+ 1/3- 1/5+....+ 1/99- 1/101)
2.A= 7.(1- 1/101)
2.A= 7.100/101
2.A= 700/101
A= 700/101: 2
A= 350/101
Vậy A= 350/101
Chúc bạn học tốt!
