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TN
2 tháng 3 2019
M= 1 + 1/2.3 + 1/3.6 + 1/4.10 +.....+ 1/16.136
M=1 + 3/2 + 2 + 5/2 +...+ 17/2
M= 2/2 + 3/2 + 4/2 + 5/2 +...+ 17/2
M=\(\frac{2+3+4+5+...+17}{2}\)
M= 152/2=76
1 tháng 11 2016
\(=1+\frac{3}{2}+2+\frac{5}{2}+3+\frac{7}{2}+...+8+\frac{17}{2}\)
\(=\left(1+2+...+8\right)+\left(\frac{3}{2}+\frac{5}{2}+...+\frac{17}{2}\right)=36+\frac{80}{2}=36+40=76\)
1 tháng 11 2016
\(B=1+\frac{1}{2}\left(1+2\right)+\frac{1}{3}\left(1+2+3\right)+\frac{1}{4}\left(1+2+3+4\right)+...+\frac{1}{16}.\left(1+2+3+...+16\right)\)
\(B=1+\frac{1}{2}.\frac{\left(1+2\right).2}{2}+\frac{1}{3}.\frac{\left(1+3\right).3}{2}+\frac{1}{4}.\frac{\left(1+4\right).4}{2}+...+\frac{1}{16}.\frac{\left(1+16\right).16}{2}\)
\(B=1+\frac{1}{2}.\frac{3.2}{2}+\frac{1}{3}.\frac{4.3}{2}+\frac{1}{4}.\frac{5.4}{2}+...+\frac{1}{16}.\frac{17.16}{2}\)
\(B=1+\frac{3}{2}+\frac{4}{2}+\frac{5}{2}+...+\frac{17}{2}\)
\(B=\frac{1}{2}.\left(2+3+4+5+...+17\right)\)
\(B=\frac{1}{2}.\frac{\left(2+17\right).16}{2}=19.4=76\)
HV
2
3 tháng 12 2016
Đặt \(A=1+\frac{1}{2}\left(1+2\right)+\frac{1}{3}\left(1+2+3\right)+\frac{1}{4}\left(1+2+3+4\right)+...+\frac{1}{16}\left(1+2+3+...+16\right)\)
\(A=1+\frac{1+2}{2}+\frac{1+2+3}{3}+\frac{1+2+3+4}{4}+...+\frac{1+2+3+...+16}{16}\)
\(A=1+\frac{2\left(2+1\right):2}{2}+\frac{3\left(3+1\right):2}{3}+\frac{4\left(4+1\right):2}{4}+...+\frac{16\left(16+1\right):2}{16}\)
\(A=1+\frac{2+1}{2}+\frac{3+1}{2}+\frac{4+1}{2}+...+\frac{16+1}{2}\)
\(A=\frac{2}{2}+\frac{3}{2}+\frac{4}{2}+\frac{5}{2}+...+\frac{17}{2}\)
\(A=\frac{2+3+4+5+...+17}{2}\)
\(A=\frac{152}{2}\)
\(A=76\)
13 tháng 9 2018
A = 1 + 1/2.(1+2) + 1/3.(1+2+3) + 1/4.(1+2+3+4) + ...+ 1/16.(1+2+....+16)
A = 1 + 1/2.3 + 1/3.6 + 1/4.10 + ...+ 1/16.136
A = 1 + 3/2 + 4/2 + 5/2 + ....+ 17/2
A = 1 + (3+4+5+...+17)/2
A = 1 + 150/2
A = 1 + 75
A = 76
13 tháng 9 2018
A = 1 + 1/2.(1+2) + 1/3.(1+2+3) + 1/4.(1+2+3+4) + ...+ 1/16.(1+2+....+16)
A = 1 + 1/2.3 + 1/3.6 + 1/4.10 + ...+ 1/16.136
A = 1 + 3/2 + 4/2 + 5/2 + ....+ 17/2
A = 1 + (3+4+5+...+17)/2
A = 1 + 150/2
A = 1 + 75
A = 76
7 tháng 2 2017
\(1+\frac{1}{2}\left(1+2\right)+\frac{1}{3}\left(1+2+3\right)+\frac{1}{4}\left(1+2+3+4\right)+...+\frac{1}{16}\left(1+2+3+...+16\right)\)
\(=1+\frac{1}{2}.\frac{2.3}{2}+\frac{1}{3}.\frac{3.4}{2}+\frac{1}{4}.\frac{4.5}{2}+...+\frac{1}{16}.\frac{16.17}{2}\)
\(=\frac{2}{2}+\frac{3}{2}+\frac{4}{2}+\frac{5}{2}+...+\frac{17}{2}\)
\(=\frac{\frac{17.18}{2}-1}{2}=76\)
g
jv tr
mất cả năm để trả lời
Sửa đề: \(1+\frac12\left(1+2\right)+\frac13\left(1+2+3\right)+\frac14\left(1+2+3+4\right)+\cdots+\frac{1}{16}\left(1+2+\cdots+16\right)\)
Ta có: \(1+\frac12\left(1+2\right)+\frac13\left(1+2+3\right)+\frac14\left(1+2+3+4\right)+\cdots+\frac{1}{16}\left(1+2+\cdots+16\right)\)
\(=1+\frac12\cdot\frac{2\cdot3}{2}+\frac13\cdot\frac{3\cdot4}{2}+\cdots+\frac{1}{16}\cdot\frac{16\cdot17}{2}\)
\(=1+\frac32+\frac42+\cdots+\frac{17}{2}=\frac{2+3+\cdots+17}{2}\)
\(=\frac{\left(17-2+1\right)\cdot\frac{\left(17+2\right)}{2}}{2}=\frac{16\cdot\frac{19}{2}}{2}=\frac{8\cdot19}{2}=19\cdot4=76\)