Tính tổng sau: A= 8 /3.5 + 8/ 5.7 +...+ 8/ 27.29
BM
Những câu hỏi liên quan
tính tổng sau
M=2/1.3+2/3.5+2/5.7+...+2/99.101
A=7/10.11+7/11.12+7/12+13+...7/69.70
B=1/25.27+1/27.29+1/29.31+...+1/73.75
Tính :
a) \(M=\frac{2}{1.3}+\frac{2}{3.5}+\frac{2}{5.7}+...+\frac{2}{99.101}\)
\(=1-\frac{1}{3}+\frac{1}{3}-\frac{1}{5}+\frac{1}{5}-\frac{1}{7}+...+\frac{1}{99}-\frac{1}{101}\)
\(=1-\frac{1}{101}\)
\(=\frac{100}{101}\)
b) \(A=\frac{7}{10.11}+\frac{7}{11.12}+\frac{7}{12.13}+...+\frac{7}{69.70}\)
\(=7.\left(\frac{1}{10.11}+\frac{1}{11.12}+\frac{1}{12.13}+...+\frac{1}{69.70}\right)\)
\(=7.\left(\frac{1}{10}-\frac{1}{11}+\frac{1}{11}-\frac{1}{12}+\frac{1}{12}-\frac{1}{13}+...+\frac{1}{69}-\frac{1}{70}\right)\)
\(=7.\left(\frac{1}{10}-\frac{1}{70}\right)\)
\(=7.\frac{3}{35}\)
\(=\frac{3}{5}\)
c) \(B=\frac{1}{25.27}+\frac{1}{27.29}+\frac{1}{29.31}+...+\frac{1}{73.75}\)
\(=\frac{1}{2}.\left(\frac{2}{25.27}+\frac{2}{27.29}+\frac{2}{29.31}+...+\frac{2}{73.75}\right)\)
\(=\frac{1}{2}.\left(\frac{1}{25}-\frac{1}{27}+\frac{1}{27}-\frac{1}{29}+\frac{1}{29}-\frac{1}{31}+...+\frac{1}{73}-\frac{1}{75}\right)\)
\(=\frac{1}{2}.\left(\frac{1}{25}-\frac{1}{75}\right)\)
\(=\frac{1}{2}.\frac{2}{75}\)
\(=\frac{1}{75}\)
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M=2/1.3+2/3.5+2/5.7+...+2/99.101
=1-1/3+1/3-1/5+1/5-1/7+...+1/99-1/101
=1-1/101
=101/101-1/101
M = 99/101
A=7/10.11+7/11.12+7/12+13+7/69/70 ( sai đề )
B= 1/25.27+1/27.29+1/29.31+...+1/73.75
=1/2.(2/25.27+2/27.29+2/29.31+...+2/73.75
=1/2.(1/25-1/27+1/27-1/29+1/29-1/31+...+1/73-1/75
=1/2.(1/25-1/75)
=1/2.75/100
=3/8
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Tính A=2/1.3-4/3.5+6/5.7-8/7.9+...-20/19.21
Mk cần gấp lắm!Ai nhanh thì mk cho 3 tích!Tính tổng sau: F=\(\frac{8}{1.3}+\frac{8}{3.5}+\frac{8}{5.7}+...+\frac{8}{2017.2019}\) H=\(\frac{1}{8.7}+\frac{1}{14.10}+\frac{1}{20.13}+\frac{1}{26.16}+\frac{1}{32.19}+\frac{1}{38.22}\)
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Tính các tổng sau
1 :D = 1.3 +2.3+3.4+........+99.100
2 . E= 1.3 +3.5+5.7+.........+97.99
3.F= 2.4 + 4.6+ 6+8+..........+98.1009
4. G=1.4+2.5+3.6+........+97.100
Giúp mình nhé . Mình cần gấp
A=\(\dfrac{4}{3.5}-\dfrac{6}{5.7}+\dfrac{8}{7.9}-\dfrac{10}{9.11}+\dfrac{12}{11.13}-...-\dfrac{100}{99.100}\)
Tính giá trị của A
tính
a,(1+8/10).(1+8/22).(1+8/36).(1+8/52)................(1+8/8352)
b,2.4+3.5+4.6+5.7+6.8+...............+97.99+98.100
tìm GTNN của A= |x^2+5| +(2y-3)\(^4\)
HL
27 tháng 5 2022 lúc 11:13
Bài 12: So sánh S = \(\dfrac{2}{1.3}+\dfrac{2}{3.5}+\dfrac{2}{5.7}+...+\dfrac{2}{27.29}+\dfrac{2}{29.31}\)
P = \(\dfrac{2014}{2015}\)
\(S=\dfrac{2}{1\cdot3}+\dfrac{2}{3\cdot5}+\dfrac{2}{5\cdot7}+...+\dfrac{2}{29\cdot31}\\ =\dfrac{1}{1}-\dfrac{1}{3}+\dfrac{1}{3}-\dfrac{1}{5}+...+\dfrac{1}{29}-\dfrac{1}{31}\\ =\dfrac{1}{1}-\dfrac{1}{31}\\ =\dfrac{30}{31}\)
mà \(\dfrac{30}{31}>\dfrac{2014}{2015}\Rightarrow S>P\)
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So sánh vs j nhỉ .-.?
`S=1-1/3+1/3-1/5+...+1/29-1/31`
`S=1-1/31=30/31`
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S=2.(1/1-1/3+1/3-1/5+1/5-1/7+...+1/27-1/29+1/29-1/31)
S=2.(1-1/31)
S=2.30/31
S=60/31
P=2014/2015
=>S>P hay 60/31 > 2014 / 2015
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Tính giá trị biêut hức;B=2/1.3-4/3.5+6/5.7-8/7.9+...-96/95.97+98/97.99
HL
18 tháng 5 2022 lúc 9:29
So sánh S và P.
Biết S = \(\dfrac{2}{1.3}+\dfrac{2}{3.5}+\dfrac{2}{5.7}+...+\dfrac{2}{27.29}+\dfrac{2}{29,31}\)
và P = \(\dfrac{2014}{2015}\)
\(S=1-\dfrac{1}{3}+\dfrac{1}{3}-\dfrac{1}{5}+\dfrac{1}{5}-\dfrac{1}{7}+...+\dfrac{1}{29}-\dfrac{1}{31}=1-\dfrac{1}{31}=\dfrac{30}{31}\)
P=2014/2015=1-1/2015
mà 1/31>1/2015
nên S<P
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