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\(\frac{1}{2}+\frac{5}{6}+\frac{11}{12}+\frac{19}{20}+\frac{29}{30}+\frac{41}{42}+\frac{55}{56}+\frac{71}{72}+\frac{89}{90}\) \(\frac{89}{90}\)
\(=(1-\frac{1}{2})+\left(1-\frac{1}{6}\right)+\left(1-\frac{1}{12}\right)+\left(1-\frac{1}{20}\right)+\left(1-\frac{1}{30}\right)+\left(1-\frac{1}{42}\right)+\left(1-\frac{1}{56}\right)\) \(+\left(1-\frac{1}{72}\right)+\left(1-\frac{1}{90}\right)\)
\(=\left(1+1+1+1+1+1+1+1+1\right)-\left(\frac{1}{2}+\frac{1}{6}+\frac{1}{12}+\frac{1}{20}+\frac{1}{30}+\frac{1}{42}+\frac{1}{56}+\frac{1}{72}+\frac{1}{90}\right)\)
\(=9-\left(\frac{1}{1.2}+\frac{1}{2.3}+\frac{1}{3.4}+\frac{1}{4.5}+\frac{1}{5.6}+\frac{1}{6.7}+\frac{1}{7.8}+\frac{1}{8.9}+\frac{1}{9.10}\right)\)
\(=9-\frac{11}{10}\)
\(=\frac{79}{10}\)
~Học tốt nha~
Đặt : \(A=\frac{1}{2}+\frac{5}{6}+\frac{11}{12}+\frac{19}{20}+\frac{29}{30}+\frac{41}{42}+\frac{55}{56}+\frac{71}{72}+\frac{89}{90}\)
\(\Leftrightarrow A=\left(1-\frac{1}{2}\right)+\left(1-\frac{1}{6}\right)+......+\left(1-\frac{1}{90}\right)\)
\(\Leftrightarrow A=\left(1+1+....+1\right)-\left(\frac{1}{2}+\frac{1}{6}+....+\frac{1}{90}\right)\)
\(\Leftrightarrow A=9-\left(\frac{1}{2.3}+\frac{1}{3.4}+...+\frac{1}{9.10}\right)\)
\(\Leftrightarrow A=9-\left(1-\frac{1}{10}\right)\)
\(\Leftrightarrow A=9-\frac{9}{10}=\frac{81}{90}\)
bn vào câu hỏi tương tự sẽ có chi tiết . Nếu k thì bn hãy để ý mỗi tử đều bé hơn mẫu 1 đơn vị sau đó bn tách ra bằng cách lấy 1 trừ . VD: 5/6 bằng 1 - 1/6 . Đến đó đếm đc 9 chữ số 1 ta lấy 9 làm sbt trừ đi tổng của các ps ta tách đc . Khi đó thì bài toán quá đơn giản rồi . Chúc bn học tốt
(1-1/2)+(1-1/6)+...+(1-1/90)
9+(1/2+1/6+...+1/90)
9+(1/1.2+1/2.3+...+1/9.10)
9+1-9/10=9/1/10=91/10
\(\frac{5}{6}+\frac{11}{12}+\frac{19}{20}+\frac{29}{30}+\frac{41}{42}+\frac{55}{56}+\frac{71}{72}+\frac{89}{90}\)
\(=1-\frac{1}{6}+1-\frac{1}{12}+1-\frac{1}{20}+1-\frac{1}{30}+1-\frac{1}{42}+1-\frac{1}{56}+1-\frac{1}{72}+1-\frac{1}{90}\)
\(=8-\left(\frac{1}{6}+\frac{1}{12}+\frac{1}{20}+\frac{1}{30}+\frac{1}{42}+\frac{1}{56}+\frac{1}{72}+\frac{1}{90}\right)\)
\(=8-\left(\frac{1}{2.3}+\frac{1}{3.4}+\frac{1}{4.5}+\frac{!}{5.6}+\frac{1}{6.7}+\frac{1}{7.8}+\frac{1}{8.9}+\frac{1}{9.10}\right)\)
\(=8-\left(\frac{1}{2}-\frac{1}{3}+\frac{1}{3}-\frac{1}{4}+\frac{1}{4}-\frac{1}{5}+.....+\frac{1}{8}-\frac{1}{9}+\frac{1}{9}-\frac{1}{10}\right)\)
\(=8-\left(\frac{1}{2}-\frac{1}{10}\right)\)
\(=8-\frac{2}{5}=\frac{38}{5}\)
1/2+5/6+11/12+19/20+29/30+41/42+55/56+71/72+89/90
=1-1/2+1-1/6+1-1/12+1-1/20+1-1/30+1-1/42+1-1/56+1-1/72+1-1/90
=9 – (1/2+1/6+1/12+1/20+1/30+1/42+1/56+1/72+1/90)
=9 – [1/(1x2)+1/(2x3)+1/(3x4)+1/(4x5)+1/(5x6)+1/(6x7)+1/(7x8)+1/(8x9)+1/(9x10)]
=9 – ( 1-1/2+1/2-1/3+1/3-1/4+1/4-1/5+1/5-1/6+1/6-1/7+1/7-1/8+1/8-1/9+1/9-1/10)
=9 – (1 – 1/10) = 9 – 9/10
= 81/10
=(1-1/2)+(1-1/6)+(1-1/12)+...+(1-1/90)
=9-(1/2 + 5/6 + 1/12 + ... + 1/90)
=9-(1-1/2+1/2-1/3+1/3-1/4+...+1/9-1/10)
=9-(1-1/10)
=9-9/10=81/10
=(1-1/2)+(1-1/6)+(1-1/12)+.......+(1-1/90)
= 9 - (1/2 +5/6 +1/12+.......+1/90)
= 9- (1-1/2 + 1/2 - 1/3+1/3 -1/4 +....... +1/9-1/10)
=9-(1-1/10)
=9-9/10=81/10
=(1-1/2)+(1-1/6)+(1-1/12)+.......+(1-1/90)
= 9 - (1/2 +5/6 +1/12+.......+1/90)
= 9- (1-1/2 + 1/2 - 1/3+1/3 -1/4 +....... +1/9-1/10)
=9-(1-1/10)
=9-9/10=81/10
Dấu \(.\)là dấu nhân
Ta có :
\(\frac{1}{2}+\frac{5}{6}+\frac{11}{12}+\frac{19}{20}+\frac{29}{30}+\frac{41}{42}+\frac{55}{56}+\frac{71}{72}+\frac{89}{90}\)
\(=\left(1-\frac{1}{2}\right)+\left(1-\frac{1}{6}\right)+\left(1-\frac{1}{12}\right)+...+\left(1-\frac{1}{72}\right)+\left(1-\frac{1}{90}\right)\)
\(=\left(1+1+1+1+1+1+1+1+1\right)-\left(\frac{1}{2}+\frac{1}{6}+\frac{1}{12}+...+\frac{1}{72}+\frac{1}{90}\right)\)
\(=1.9-\left(\frac{1}{1.2}+\frac{1}{2.3}+\frac{1}{3.4}+...+\frac{1}{8.9}+\frac{1}{9.10}\right)\)
\(=9-\left(1-\frac{1}{2}+\frac{1}{2}-\frac{1}{3}+\frac{1}{3}-\frac{1}{4}+...+\frac{1}{8}-\frac{1}{9}+\frac{1}{9}-\frac{1}{10}\right)\)
\(=9-\left(1-\frac{1}{10}\right)\)
\(=9-\frac{9}{10}\)
\(=\frac{90}{10}-\frac{9}{10}\)
\(=\frac{81}{10}\)
~ Ủng hộ nhé
\(\frac{1}{2}+\frac{5}{6}+\frac{11}{12}+\frac{19}{20}+...+\frac{89}{90}\)
\(=1-\frac{1}{2}+1-\frac{1}{6}+1-\frac{1}{12}+1-\frac{1}{20}+...+1-\frac{1}{90}\)
\(=9-\left(\frac{1}{2}+\frac{1}{6}+\frac{1}{12}+\frac{1}{20}+...+\frac{1}{90}\right)\)
\(=9-\left(\frac{1}{1.2}+\frac{1}{2.3}+\frac{1}{3.4}+\frac{1}{4.5}+...+\frac{1}{9.10}\right)\)
\(=9-\left(1-\frac{1}{2}+\frac{1}{2}-\frac{1}{3}+\frac{1}{3}-\frac{1}{4}+....+\frac{1}{9}-\frac{1}{10}\right)\)
\(=9-\left(1-\frac{1}{10}\right)\)
\(=9-\frac{9}{10}=\frac{81}{10}\)
A=(1-1/2)+(1-1/6)+(1-1/12)+(1-1/20)+(1-1/30)+(1-1/42)+(1-1/56)+(1-1/72)+(1-1/90)
A=(1+1+1+1+1+1+1+1+1)-(1/2+1/6+1/12+1/20+1/30+1/42+1/56+1/72+1/90)
A=9-(1/1x2+1/2x3+1/3x4+1/4x5+1/5x6+1/6x7+1/7x8+1/8x9+1/9x10)
A=9-(1/1-1/2+1/2-1/3+1/3-1/4+1/4-1/5+1/5-1/6+1/6-1/7+1/7-1/8+1/8-1/9+1/9-1/10)
A=9-(1/1-1/10)
A=9-(10/10-1/10)
A=9-9/10
A=90/10-9/10
A=81/10
Tích cho mk nha
đơn giản:
\(A=\frac{1}{2}+\frac{5}{6}+\frac{11}{12}+\frac{19}{20}+\frac{29}{30}+\frac{41}{42}+\frac{55}{56}+\frac{71}{72}+\frac{89}{90}\)
\(A=\left(1-\frac{1}{2}\right)+\left(1-\frac{1}{6}\right)+\left(1-\frac{1}{12}\right)+.....+\left(1-\frac{1}{90}\right)\)
\(A=\left(1+1+1+.....+1\right)-\left(\frac{1}{2}+\frac{1}{6}+....+\frac{1}{90}\right)\)
\(A=9-\left(\frac{1}{1x2}+\frac{1}{2x3}+\frac{1}{3x4}+\frac{1}{5x6}+....+\frac{1}{9x10}\right)\)
\(A=9-\left(1-\frac{1}{2}+\frac{1}{2}-\frac{1}{3}+...+\frac{1}{9}-\frac{1}{10}\right)\)
\(A=9-\left(1-\frac{1}{10}\right)\)
\(A=9-\frac{9}{10}\)
\(A=\frac{90}{10}-\frac{9}{10}\)
\(A=\frac{81}{10}\)
\(A=\frac{1}{2}+\frac{5}{6}+\frac{11}{12}+\frac{19}{20}+\frac{29}{30}+\frac{41}{42}+\frac{55}{56}+\frac{71}{72}+\frac{89}{90}\)
\(A=1-\frac{1}{2}+1-\frac{1}{6}+1-\frac{1}{12}+1-\frac{1}{20}+1-\frac{1}{30}+1-\frac{1}{41}+1\)\(-\frac{1}{56}+1-\frac{1}{72}+1-\frac{1}{90}\)
\(A=9-\left(\frac{1}{2}+\frac{1}{6}+\frac{1}{12}+\frac{1}{20}+\frac{1}{30}+\frac{1}{42}+\frac{1}{56}+\frac{1}{72}+\frac{1}{90}\right)\)
\(A=9-\left[1\div\left(1\times2\right)+1\div\left(2\times3\right)+1\div\left(3\times4\right)+1\div\left(4\times5\right)\right]\)\(+1\div\left(5\times6\right)+1\div\left(6\times7\right)+1\div\left(7\times8\right)+1\div\left(8\times9\right)\)\(+1\div\left(9\times10\right)\)]
\(A=9-\left(1-\frac{1}{2}+\frac{1}{2}-\frac{1}{3}+\frac{1}{3}-\frac{1}{4}+\frac{1}{4}-\frac{1}{5}+\frac{1}{5}-\frac{1}{6}\right)\)\(+\frac{1}{6}-\frac{1}{7}+\frac{1}{7}-\frac{1}{8}+\frac{1}{8}-\frac{1}{9}+\frac{1}{9}-\frac{1}{10}\))
\(A=9-\left(1-\frac{1}{10}\right)\)
\(A=9-\frac{9}{10}\)
\(A=\frac{81}{10}\)
\(A=1+1+...+1-\left(\frac{1}{2}+\frac{1}{6}+...+\frac{1}{90}\right)\)
\(A=9-\left(\frac{1}{1.2}+\frac{1}{2.3}+...+\frac{1}{9.10}\right)\)
\(A=9-\left(\frac{2-1}{1.2}+\frac{3-2}{2.3}+...+\frac{10-9}{10.9}\right)\)
\(A=9-\left(1-\frac{1}{2}+\frac{1}{2}-\frac{1}{3}+...+\frac{1}{9}-\frac{1}{10}\right)\)
\(A=9-\frac{9}{10}=\frac{81}{10}\)
cho hỏi viết phân số kiểu gì???????
Theo đề bài , ta thấy mẫu số có quy luật là số ở sau = số ở trước nhân với 4,6,8,10,...45 còn tử số có quy luật là số ở sau = số ở trước + 4,6,8,10,...Nên ta có mẫu số chung là 90 .
\(\frac{1}{2}+\frac{5}{6}+\frac{11}{12}+\frac{19}{20}+\frac{29}{30}+\frac{41}{42}+\frac{55}{56}+\frac{71}{72}+\frac{89}{90}\) = \(\frac{463,75}{90}+\frac{41}{42}+\frac{55}{56}\)=\(\frac{64}{9}\)
Ta có: A = 1/2 + 5/6 + 11/12 + 19/20 + 29/30 + 41/42 + 55/56 + 71/72 + 89/90
= (1 - 1/2) + (1 - 1/6) + (1 - 1/12) + (1 - 1/20) + (1 - 1/30) + (1 - 1/42) + (1 - 1/56) + (1 - 1/72) + (1 - 1/90)
= (1 + 1 + 1 + 1 + 1 +1 +1 +1 +1) - (1/2 + 1/6 + 1/12 + 1/ 20 + 1/30 + 1/42 + 1/56 + 1/72 + 1/90)
= 9 - ( 1/1.2+1/2.3 + 1/3.4 + 1/4.5 + 1/5.6 + 1/6.7 + 1/7.8 + 1/8.9 + 1/9.10
= 9 - (1 - 1/2 + 1/2 - 1/3 + 1/3 - 1/4 + 1/4 -1/5 + 1/5 - 1/6 +1/6 - 1/7 + 1/7 - 1/8 + 1/8 - 1/9 + 1/9 - 1/10
= 9 - ( 1 - 1/10)
= 9 - 9/10
= 81/10
Mk lười viết phân số lắm +_+
A = 1/1x2 + 1/2x3 + 1/3x4 + 1/4x5 + 1/5x6 + 1/6x7 +1/7x8 + 1/8x9 + 1/9x10
A = 1/1 - 1/2 + 1/2 - 1/3 + 1/3 - 1/4 + 1/4 - 1/5 + 1/5 - 1/6 + 1/6 - 1/7 + 1/7 - 1/8 + 1/8 - 1/9 + 1/9 - 1/10
A = 1/1 - 1/10
A = 10/11 - 1/10 = 9/10
Vậy A = 9/10
Hu hu ! Bài này thằng nhỏ ( mình ) giải đuối đừ mà ko được tích
\(A=\frac{1}{2}+\frac{5}{6}+\frac{11}{12}+...+\frac{89}{90}\)
\(A=\left(1-\frac{1}{2}\right)+\left(1-\frac{1}{6}\right)+\left(1-\frac{1}{12}\right)+...+\left(1-\frac{1}{90}\right)\)
\(A=1-\frac{1}{2}+1-\frac{1}{6}+1-\frac{1}{12}+...+1-\frac{1}{90}\)
\(A=\left(1+1+1+...+1\right)-\left(\frac{1}{2}+\frac{1}{6}+\frac{1}{12}+...+\frac{1}{90}\right)\)
\(A=9-\left(\frac{1}{1.2}+\frac{1}{2.3}+\frac{1}{3.4}+...+\frac{1}{9.10}\right)\)
\(A=9-\left(\frac{1}{1}-\frac{1}{2}+\frac{1}{2}-\frac{1}{3}+\frac{1}{3}-\frac{1}{4}+...+\frac{1}{9}-\frac{1}{10}\right)\)
\(A=9-\left(1-\frac{1}{10}\right)\)
\(A=9-\frac{8}{9}\)
\(A=\frac{73}{9}\)
A=12 +56 +1112 +1920 +2930 +4142 +5556 +7172 +8990
A=1−12 +1−16 +1−112 +1−120 +1−130 +1−141 +1−156 +1−172 +1−190
A=9−(12 +16 +112 +120 +130 +142 +156 +172 +190 )
A=9−[1÷(1×2)+1÷(2×3)+1÷(3×4)+1÷(4×5)]+1÷(5×6)+1÷(6×7)+1÷(7×8)+1÷(8×9)+1÷(9×10)]
A=9−(1−12 +12 −13 +13 −14 +14 −15 +15 −16 )+16 −17 +17 −18 +18 −19 +19 −110 )
A=9−(1−110 )
A=9−910
A=8110
(1-1/2)+(1-1/6)+(1-1/12)+....+(1-1/90)+(1-1/110)
1*10+(1/1*2)+(1/2*3)+(1/3*4)+......+(1/9*10)+(1/10*11)
10-(1-1/11)
10-10/11
100/11
bài này dễ ợt ko ak!!!!!!!!!!!!!
bạn bấm máy tính cầm tay là oki luôn!
ai đồng tình thì k cho mk nha =)
thanks :)
81/10 nha bn
lan truoc tui cung lam, biet gi dau,ra 81/10 do
mink ko có thời gian để gõ nhưng mik nghĩ kết quả = 81/10
A = 81/10
mả cha bây ả
A=1-1/2+1-1/6+1-1/12+1-1/20+.......+1-1/72+1-1/90 =>A=(1+1+...+1+1)-(1/2+1/6+......+1/72+1/90)
A=9-(1/1.2+1/2.3+1/3.4+......+1/8.9+1/9.10)
A=9-(1-1/2+1/2-1/3+......+1/8-1/9+1/9-1/10)
A=9-(1-1/10)
A=9-9/10
A=81/10
A=8,1
A = 1/2 + 5/6 + 11/12 + 19/20 + 29/30 + 41/42 + 55/56 + 71/72 + 89/90
Đa số toàn chép bài nhau
-Ta có: 1/2+5/6+11/12+...+89/90
= ( 1/2+5/6+11/12+...+89/90+1/2+1/6+1/12+....+1/90)-(1/2+1/6+1/12+....+1/90)
= (1+1+1+...+1)-(1/1*2+1/2*3+1/3*4+...+1/9*10)
(9 số hạng 1)
=9-(1-1/2+1/2-1/3+1/3-1/4+...+1/9-1/10)
=9-9/10=81/10
81/10
A=(1-1/2)+(1-1/6)+(1-1/12)+(1-1/20)+(1-1/30)+(1-1/42)+(1-1/56)+(1-1/72)+(1-1/90)
=9-(1/2+1/6+1/12+1/20+1/30+1/42+1/56+1/72+1/90)
=9-(1/2+1/2-1/3+1/3-1/4+1/4-1/5+1/5-1/6+1/6-1/7+1/7-1/8+1/8-1/9+1/9-1/10)
=9-9/10=81/10
ko bít
A=8,1
Vì tớ không viết hân số được nên viết số thập phân
Các bạn nha!
Cảm ơn nhìu!
kinh chưa
81/10