1/1.2+1/2.3+1/3.4+...+1/x.(x+1)=2022/2021
giúp mk với mn oiiiiiiiiiiiiii !!!!!!!!!!!!!!!!!
Những câu hỏi liên quan
\(\dfrac{1}{1.2}+\dfrac{2}{2.3}+\dfrac{1}{3.4}+...+\dfrac{1}{x.(x+1)}=\dfrac{2021}{2022}\)
\(\Leftrightarrow1-\dfrac{1}{2}+\dfrac{1}{2}-\dfrac{1}{3}+...+\dfrac{1}{x}-\dfrac{1}{x+1}=\dfrac{2021}{2022}\)
\(\Leftrightarrow1-\dfrac{1}{x+1}=\dfrac{2021}{2022}\)
\(\Leftrightarrow\dfrac{1}{x+1}=\dfrac{1}{2022}\)
=>x+1=2022
hay x=2021
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So sánh A=2021/2022 và B=1/1.2+1/2.3+1/3.4+2...+1/97.98+1/98.99
\(B=\dfrac{1}{1.2}+\dfrac{1}{2.3}+\dfrac{1}{3.4}+...+\dfrac{1}{98.99}\)
\(=\dfrac{2-1}{1.2}+\dfrac{3-2}{2.3}+\dfrac{4-3}{3.4}+...+\dfrac{99-98}{98.99}\)
\(=1-\dfrac{1}{2}+\dfrac{1}{2}-\dfrac{1}{3}+\dfrac{1}{3}-\dfrac{1}{4}+...+\dfrac{1}{98}-\dfrac{1}{99}\)
\(=1-\dfrac{1}{99}\)
\(A=\dfrac{2021}{2022}=\dfrac{2022-1}{2022}=1-\dfrac{1}{2022}\)
Có \(2022>99>0\Leftrightarrow\dfrac{1}{99}>\dfrac{1}{2022}\)
Suy ra \(A>B\).
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giúp mìn với 1/1.2 +1/2.3+1/3.4+1/4.5+....+1/[x-1].x+1/x.[x+1]
Tìm x biết :
1/1.2+1/2.3+1/3.4+...+1/(x-1)x+1/x(x+1)=2016/2017
(Trình bày đầy đủ cách làm mk tick)
đặt A=.....
=\(1-\frac{1}{2}+\frac{1}{2}-\frac{1}{3}+....+\frac{1}{x-1}-\frac{1}{x}+\frac{1}{x}-\frac{1}{x+1}\)=\(\frac{2016}{2017}\)
=\(1-\frac{1}{x+1}=\frac{2016}{2017}\)
=\(\frac{x}{x+1}=\frac{2016}{2017}\)
=>x=2016
vậy..............
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Tìm x : |x+1/1.2|+|x+1/2.3|+|x+1/3.4|+...+|x+2016.2017|=2017xGiúp mình với ! Cảm ơn
|x+1/1.2|+|x+1/2.3|+|x+1/3.4|+.........+|x+1/2020.2021|=2021x
Xem chi tiết
(x+1/1.2)+(x+1/2.3)+(x+1/3.4)+....+(x+1/2022.2023)=2023x
\(\Rightarrow\left(x+x+...+x\right)+\left(\dfrac{1}{1.2}+\dfrac{1}{2.3}+\dfrac{1}{3.4}+...+\dfrac{1}{2022.2023}\right)=2023x\)
\(\Rightarrow2022x+\left(\dfrac{1}{1}-\dfrac{1}{2}+\dfrac{1}{2}-\dfrac{1}{3}+\dfrac{1}{3}-\dfrac{1}{4}+\dfrac{1}{4}-...-\dfrac{1}{2021}+\dfrac{1}{2021}-\dfrac{1}{2022}+\dfrac{1}{2022}-\dfrac{1}{2023}\right)=2023x\)\(\Rightarrow2022x-2023x=-\left(1-\dfrac{1}{2023}\right)\)
\(\Rightarrow-x=-\dfrac{2022}{2023}\Leftrightarrow x=\dfrac{2022}{2023}\)
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(x + 1/1.2) + (x + 1/2.3) + (x + 1/3.4) + ... + (x + 1/2022.2023) = 2023x
x + x + x + ... + x + 1/1.2 + 1/2.3 + ... + 1/2022.2023 = 2023x
2022x + 1 - 1/2 + 1/2 - 1/3 + ... + 1/2022 - 2023 = 2023x
2023x - 2022x = 1 - 1/2023
x = 2022/2023
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B=\(\frac{1}{1.2}+\frac{1}{2.3}+\frac{1}{3.4}+...+\frac{1}{x.\left(x+1\right)}\)(x thuộc Z)
tính B
các bn giúp mk nhé mk tk
\(\frac{1}{1.2}+\frac{1}{2.3}+...+\frac{1}{x.\left(x+1\right)}\)
\(=1-\frac{1}{2}+\frac{1}{2}-\frac{1}{3}+...+\frac{1}{x}-\frac{1}{x+1}\)
\(=1-\frac{1}{x+1}=\frac{x+1}{x+1}-\frac{1}{x+1}=\frac{x}{x+1}\)
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Xem thêm câu trả lời
1, tìm x thuộc N biết
32+42=5x-1
2, tính tổng
S=1.2+2.3+3.4+...+99.100
S=1.2+2.3+3.4+...+99.100
giúp mình nha mình đang cần gấp,thanks mn
1. ta có :
\(3^2+4^2=5^{x-1}\)
\(25=5^{x-1}\)
\(5^2=5^{x-1}\)
=> x = 3
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Ta có : S = 1.2 + 2.3 + 3.4 + ..... + 99.100
=> 3S = 1.2.3 - 1.2.3 + 2.3.4 - 2.3.4 + ..... + 99.100.101
=> 3S = 99.100.101
=> S = 99.100.101/3
=> S = 333300
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