A = ( 3/1.8 + 3/8.15 + 3/15.22 +...+ 3/106.113 ) - ( 25/50.55 + 25/55.60 +...+ 25/95.100 )
Những câu hỏi liên quan
\(\left(\frac{3}{1.8}+\frac{3}{8.15}+\frac{3}{15.22}+...+\frac{3}{106.113}\right)-\left(\frac{25}{50.55}+\frac{25}{55.60}+...+\frac{25}{95.100}\right)\)
Giải giúp mk với!
\(A=\frac{3}{1.8}+\frac{3}{8.15}+\frac{3}{15.22}+...+\frac{3}{106.113}\)
\(=\frac{3}{7}\left(\frac{7}{1.8}+\frac{7}{8.15}+\frac{7}{15.22}+...+\frac{7}{106.113}\right)\)
\(=\frac{3}{7}\left(\frac{8-1}{1.8}+\frac{15-8}{8.15}+\frac{22-15}{15.22}+...+\frac{113-106}{106.113}\right)\)
\(=\frac{3}{7}\left(1-\frac{1}{8}+\frac{1}{8}-\frac{1}{15}+\frac{1}{15}-\frac{1}{22}+\frac{1}{106}-\frac{1}{113}\right)\)
\(=\frac{3}{7}\left(1-\frac{1}{113}\right)=\frac{48}{113}\)
\(B=\frac{25}{50.55}+\frac{25}{55.60}+...+\frac{25}{95.100}\)
\(=5\left(\frac{5}{50.55}+\frac{5}{55.60}+...+\frac{5}{95.100}\right)\)
\(=5\left(\frac{55-50}{50.55}+\frac{60-55}{55.60}+...+\frac{100-95}{95.100}\right)\)
\(=5\left(\frac{1}{50}-\frac{1}{55}+\frac{1}{55}-\frac{1}{60}+...+\frac{1}{95}-\frac{1}{100}\right)\)
\(=5\left(\frac{1}{50}-\frac{1}{100}\right)=\frac{1}{20}\)
Giá trị của biểu thức đã cho là:
\(A-B=\frac{48}{113}-\frac{1}{20}=\frac{847}{2260}\)
Tính:
F=(\(\frac{3}{1.8}+\frac{3}{8.15}+\frac{3}{15.22}+....+\frac{3}{106.113}\) ) - (\(\frac{25}{50.55}+\frac{25}{55.60}+\frac{25}{60.65}+.....+\frac{25}{95.100}\))
F=(3/1.8+3/8.15+...+3/106.113)-(25/50.55+25/55.60+...+25/95.100) (1)
Đặt:
A=(3/1.8+3/8.15+3/15.22+...+3/106.113)
=3/7.(1-1/8+1/8-1/15+...+1/106-1/113)
=3/7.(1-1/113)
=3/7.112/113
=336/791. (2)
B=25/50.55+25/55.60+...+25/95.100
=25/5.(1/50-1/55+1/55-1/60+...+1/95-1/100)
=5.(1/50-1/100)
=1/20 (3)
Thay (2),(3) vào (1) ta được:
F=336/791-1/20
=5929/6720.
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1.
a) \(\text{(3x-5)6=(3x-5)4}\)
2.
a)\(\frac{2}{7}.\frac{2012}{2011}-\frac{2}{2011}.\frac{1}{7}_{ }+\frac{4}{7}\)
b) \(\left(\frac{3}{1.8}+\frac{3}{8.15}+\frac{3}{15.22}+...+\frac{3}{106.113}\right)-\left(\frac{25}{50,55}\frac{25}{55.60}\frac{25}{60.65}...\frac{25}{95.100}\right)\)
ai nhanh đúng mk tk
tính F=7/1.8+7/8.15+7/15.22+...+7/n.(n+7)
F=7/1.8+7/8.15+7/15.22+...+7/n.(n+7)
=1/1-1/8+1/8-1/15+1/15-1/22+...+1/n-1/n+7
=1/1-1/n+7
=n+7/n+7-1/n+7
=n+7-1/n+7
=n+6/n+7
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Bài 3: Rút gọn các phân số sau:
a) \(\dfrac{10.11+50.55+70.77}{11.12+55.60+77.84}\)
b) \(\dfrac{2^{19}.27^3+15.4^9.9^4}{6^9.2^{10}+12^{10}}\)
(Tớ cần lời giải tính nhanh và hợp lý ạ,giúp tớ vớii)
A= \(\dfrac{10.11.\left(1+5.5+7.7\right)}{11.12.\left(1+5.5+7.7\right)}=\dfrac{10}{12}=\dfrac{5}{6}\)
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tính (1/8+1/8.15+1/15.22+....+1/43.50)x(4-3-5-7-...-49)/217
Bài 5: Thực hiện phép tính:a) 47 – [(45.24 – 52.12):14]a) 3.52 + 15.22 – 26:2b) 50 – [(20 – 23) : 2 + 34]b) (- 25) . (- 4 ) + (- 70) . 3c) 102 – [60 : (56 : 54 – 3.5)]c) 62 : (- 9) - 50.2 – 33.(- 3)d) 50 – [(50 – 23.5):2 + 3]d) 32.(- 50) - 23.10 – 81: (- 3)e) 10 – [(82 – 48).5 + (23.10 + 8)] : 28e) 513 : 510 – 25.22f) 8697 – [37 : 35 + 2(13 – 3)]f) 20 : 22 + 59 : 58g) 2011 + 5[300 – (17 – 7)2]g) 100 : 52 + 7.32h) 695 – [200 + (11 – 1)2]h) 84 : 4 + 39 : 37 + 50i) 129 – 5[29 – (6 – 1)2]i) 29 –...
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Bài 5: Thực hiện phép tính:
a) 47 – [(45.24 – 52.12):14] | a) 3.52 + 15.22 – 26:2 |
b) 50 – [(20 – 23) : 2 + 34] | b) (- 25) . (- 4 ) + (- 70) . 3 |
c) 102 – [60 : (56 : 54 – 3.5)] | c) 62 : (- 9) - 50.2 – 33.(- 3) |
d) 50 – [(50 – 23.5):2 + 3] | d) 32.(- 50) - 23.10 – 81: (- 3) |
e) 10 – [(82 – 48).5 + (23.10 + 8)] : 28 | e) 513 : 510 – 25.22 |
f) 8697 – [37 : 35 + 2(13 – 3)] | f) 20 : 22 + 59 : 58 |
g) 2011 + 5[300 – (17 – 7)2] | g) 100 : 52 + 7.32 |
h) 695 – [200 + (11 – 1)2] | h) 84 : 4 + 39 : 37 + 50 |
i) 129 – 5[29 – (6 – 1)2] | i) 29 – [16 + 3.(51 – 49)] |
j) 2010 – 2000 : [486 – 2(72 – 6)] | j) 53.2 – 100 : 4 + 23.5 |
f: =20:4+5
=5+5
=10
e: =125-100=25
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Ai giúp mk vs tìm x biet a,7/x=x/28 b, 10+x/17+x=3/4 giúp mk vs ai nhanh nhất mk sẽ tick 2. Rut gọn a,10.11+50.55+70.77/11.12+55.60+77.84 giúp mk vssssss
\(a,\frac{7}{x}=\frac{x}{28}=>x\cdot x=28\cdot7=>x^2=196=>x^2=14^2\)\(=>x=14\)
\(b,\frac{10+x}{x+17}=\frac{3}{4}=>\left(10+x\right)\cdot4=\left(x+17\right)\cdot3=>40+x4=x3+51\)\(=>x4-x3=51-40=>x=11\)
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10.11+50.55+70.77/11.12+55.60+77.84 tính
Xem thêm câu trả lời
C=\(\frac{49}{1.8}\)+ \(\frac{49}{8.15}\)+ \(\frac{49}{15.22}\)+ ... + \(\frac{49}{141.148}\)
Tính giá trị biểu thức trên
\(C=\frac{49}{1.8}+\frac{49}{8.15}+\frac{49}{15.22}+...+\frac{49}{141.148}\)
\(\Rightarrow\frac{1}{7}C=\frac{7}{1.8}+\frac{7}{8.15}+\frac{7}{15.22}+...+\frac{7}{141.148}\)
\(=1-\frac{1}{8}+\frac{1}{8}-\frac{1}{15}+\frac{1}{15}-\frac{1}{22}+...+\frac{1}{141}-\frac{1}{148}\)
\(=1-\frac{1}{148}=\frac{148}{148}-\frac{1}{148}=\frac{147}{148}\)
\(\Rightarrow C=\frac{147}{148}\div\frac{1}{7}=\frac{147}{148}.7=\frac{1029}{148}\)
Vậy \(C=\frac{1029}{148}.\)
=49(1/1.8 +1/8.15+..)
có
1/1.8= (1-1/8)
1/8.15=1/8-1/15
=> C=49*1/7*(1-1/8+1/8-1/15+...+1/141-1/148)
C=7*(1-1/148)=...
học tốt
Bài làm:
Ta có: \(C=\frac{49}{1.8}+\frac{49}{8.15}+\frac{49}{15.22}+...+\frac{49}{141.148}\)
\(C=7\left(\frac{8-1}{1.8}+\frac{15-8}{8.15}+\frac{22-15}{15.22}+...+\frac{148-141}{141.148}\right)\)
\(C=7\left(1-\frac{1}{8}+\frac{1}{8}-\frac{1}{15}+\frac{1}{15}-\frac{1}{22}+...+\frac{1}{141}-\frac{1}{148}\right)\)
\(C=7\left(1-\frac{1}{148}\right)\)
\(C=7.\frac{147}{148}=\frac{1029}{148}\)
Xem thêm câu trả lời