Question

1) 1/6+1/12+1/30+1/42+1/56+1/72

2) 3/1.4+3/4.7+3/7.10+3/10.13+3/13.16

Answer 1

Nguyễn Huy Thắng giải sai rồi ,thế này mới đúng nè

1,\(\frac{1}{6}+\frac{1}{12}+.........+\frac{1}{72}\)

=\(\frac{1}{2.3}+\frac{1}{3.4}+.......+\frac{1}{8.9}\)

=\(\frac{1}{2}-\frac{1}{3}+\frac{1}{3}-\frac{1}{4}+.......+\frac{1}{8}-\frac{1}{9}\)

=\(\frac{1}{2}-\frac{1}{9}\)

=\(\frac{7}{18}\)

2,\(\frac{3}{1.4}+\frac{3}{4.7}+..........+\frac{3}{13.16}\)

=\(1-\frac{1}{4}+\frac{1}{4}-\frac{1}{7}+.........+\frac{1}{13}-\frac{1}{16}\)

=\(1-\frac{1}{16}\)

=\(\frac{15}{16}\)

Answer 2

2)đặt B= 3/1.4+3/4.7+3/7.10+3/10.13+3/13.16

\(B=3\left(1-\frac{1}{4}+\frac{1}{4}-\frac{1}{7}+...+\frac{1}{13}-\frac{1}{16}\right)\)

\(B=3-\frac{15}{16}\)

\(B=\frac{45}{16}\)

Answer 3

1)

1/6+1/12+1/30+1/56+1/72

= 1/2x3+1/3x4+1/4x5+1/5x6+1/6x7+1/7x8

= 1/2-1/3+1/3-1/4+...+1/7-1/8

= 1/2-1/8

= 3/8

2)

3/1.4+3/4.7+3/7.10+3/10.13+3/13.16

= 1-1/4+1/4-1/7+..+1/13-1/16

= 1-1/16

= 15/16

mk nhé đầu tiên đó

Answer 4

chết là 3 nhân 15/16

Answer 5

1/6+1/12+1/30+1/42+1/56+1/72 = 61/180 

3/1.4+3/4.7+3/7.10+3/10.13+3/13.16 = 15/16

úm ba la xin tích

Answer 6

Trần Thùy Trang giải tào lao 30=4*5 (troll quá mức)

Answer 7

1) 1 / 6 + 1 / 12 + 1 / 20 +1 / 30 + 1 / 42 + 1 / 56 + 1 / 72

= 1 / 2 . 3 + 1 / 3 . 4 + 1 / 4 . 5 +.....+ 1 / 8 . 9

= 1 - 1 / 2 + 1 / 2 - 1 / 3 + 1 / 4 - 1 / 5+.... + 1 / 8 - 1 / 9

= 1 - 1 / 9

= 8 / 9

2 ) 3  / 1 . 4 + 3 / 4 . 7 + 3 / 7 . 10+...+ 3 / 13 . 16

= 1 - 1 / 4 + 1 / 4 - 1 / 5 +.....+ 1 / 13 - 1 / 16

= 1 - 1 / 16

= 15 / 16

Answer 8

\(\frac{1}{6}+\frac{1}{12}+\frac{1}{30}+\frac{1}{42}+\frac{1}{56}+\frac{1}{72}\)

Thiếu đề hay sao ấy

Answer 9

Trần Minh Ngọc câu 1 kia là 1/2 mà

Answer 10

Không có học trò dốt

Mà chỉ có thầy chưa giỏi

Answer 11

alo