1/2+ 1/3 +1/4 +1/5 ... +1/49 +1/50 giai giup mik gap lm!.>..
Những câu hỏi liên quan
Cho A = 1/1.2 + 1/3.4 + 1/5.6 +.......+ 1/49.50.
B = 1 + 1/2 + 1/3 + 1/4 +........+ 1/49 + 1/50.
C = 1/2 + 1/4 + 1/6 +.........+ 1/48 + 1/50.
CMR A = B - 2C.
Minh dang can gap. Ai biet thi chi giup minh nhe ! Cam on moi nguoi nhieu lam.
A = 1/1.2 + 1/3.4 + 1/5.6 + ... + 1/49.50
A =1 - 1/2 + 1/3 - 1/4 + 1/5 - 1/6 + ... + 1/49 - 1/50
A = (1 + 1/3 + 1/5 + ... + 1/49) - (1/2 + 1/4 + 1/6 + ... + 1/50)
A = (1 + 1/2 + 1/3 + 1/4 + 1/5 + 1/6 + ... + 1/49 + 1/50) - 2.(1/2 + 1/4 + 1/6 + ... +1/50)
A = B - 2C
=> đpcm
Ủng hộ mk nha ♡_♡☆_☆
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giup mik voi can gap
Giai pt
a) 3✔x-5/2 - 2✔x-7/3 =✔x-1
b)✔36x-72 -15✔x-2/25 =4(5+✔x-2)
\
b: \(\Leftrightarrow6\sqrt{x-2}-15\cdot\dfrac{\sqrt{x-2}}{5}=20+4\sqrt{x-2}\)
\(\Leftrightarrow\sqrt{x-2}\cdot6-3\sqrt{x-2}-4\sqrt{x-2}=20\)
\(\Leftrightarrow-\sqrt{x-2}=20\)(vô lý)
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3/7:4/49
1/2-(1/3)<x<1/48-(1/16)
giup mik nhe , ai giup mik tik cho!!!!!!!!!!!!
|2x+1|+|4x+1|+|6x+1|=5
|x+1/2|+|x+1/3|+|x+1/4|=x
Giai giup mik vs😊😊
1/2×3 + 1/3×4 + 1/4×5 + ... + 1/49×50
Giải hộ mik với. Ai nhanh, đúng mik tặng 3 tick nha:))
\(\frac{1}{2\cdot3}+\frac{1}{3\cdot4}+\frac{1}{4\cdot5}+...+\frac{1}{49\cdot50}\)
\(=\frac{1}{2}-\frac{1}{3}+\frac{1}{3}-\frac{1}{4}+\frac{1}{5}-.....+\frac{1}{49}-\frac{1}{50}\)
\(=\frac{1}{2}-\frac{1}{50}\)
\(=\frac{24}{50}=\frac{12}{25}\)
\(\frac{1}{2\cdot3}+\frac{1}{3\cdot4}+\frac{1}{4\cdot5}+...+\frac{1}{49\cdot50}\)
\(=\frac{1}{2}-\frac{1}{3}+\frac{1}{3}-\frac{1}{4}+\frac{1}{4}-\frac{1}{5}+...+\frac{1}{49}-\frac{1}{50}\)
\(=\frac{1}{2}-\frac{1}{50}\)
\(=\frac{12}{25}\)
\(\frac{1}{2.3}+\frac{1}{3.4}+\frac{1}{4.5}+...+\frac{1}{49.50}\)
\(=\frac{1}{2}-\frac{1}{3}+\frac{1}{3}-\frac{1}{4}+\frac{1}{4}-\frac{1}{5}+...+\frac{1}{49}-\frac{1}{50}\)
\(=\frac{1}{2}-\frac{1}{50}\)
\(=\frac{25}{50}-\frac{1}{50}\)
\(=\frac{24}{50}=\frac{12}{25}\)
1. a) Tim so tu nhien a biet rang khi chia 39 cho a thi du 3 con chia cho 49 thi du 4
b)Tim so tu nhien x biet: 12 chia het cho ( x-2 )
c) Tim so tu nhien n biet: 1+3+5+...+(2n+1) = 72
mik dag gap lam bn nao giai dc nhanh mik tick cho
tim x,y thuoc Z
a)5x.(-x)^2+1=6
4.x^3=4x
xy=x+y
xy=x-y
giai giup mik nha mik can gap
a) 5x.(-x)2 + 1 = 6
<=> 5x.x2 = 5
<=> 5x3 = 5
<=> x3 = 1
<=> x = 1
b) 4.x3 = 4x
4x3 - 4x = 0
4x.(x2 - 1) = 0
\(\Leftrightarrow\orbr{\begin{cases}4x=0\\x^2-1=0\end{cases}}\Leftrightarrow\orbr{\begin{cases}x=0\\x^2=1\end{cases}}\)
Với \(x^2=1\)
\(\Leftrightarrow\orbr{\begin{cases}x=1\\x=-1\end{cases}}\)
c) xy = x + y
x + y - xy = 0
x + y - xy - 1 = 0
(x - xy) - (1 - y) = 0
x(1 - y) - (1 - y) = 0
(x - 1)(1 - y) = 0
\(\Leftrightarrow\orbr{\begin{cases}x-1=0\\1-y=0\end{cases}}\Leftrightarrow\orbr{\begin{cases}x=1\\y=1\end{cases}}\)
d) Tương tự
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giai giup mik vs a \(\dfrac{1}{1+\sqrt[3]{2}+\sqrt[3]{4}}\)
\(\dfrac{1}{\sqrt[3]{4}+\sqrt[3]{2}+1}=\dfrac{\sqrt[3]{2}-1}{\left(\sqrt[3]{2}-1\right)\left(\sqrt[3]{4}+\sqrt[3]{2}+1\right)}\)
\(=\dfrac{\sqrt[3]{2}-1}{2-1}=\sqrt[3]{2}-1\)
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Tính nhanh:
a= (502+482+462+...+42+22)-(492+472+452+...+52+32+12)
b=2004.2006.(20052+1)
c=(2+1).(22+1).(24+1).(28+1)
mk dag cab gap. cac p giup mk nha.THANKS
1 tim x , biet
a) x - 7va 5/8 = 1 va 1/4
b) x + 7 va 5/8 = 9 va 1/4
c) ( x - 7 va 5/8 ) : 1/2 = 3
d) x / 1x3 + x/3x5+.....+x/97x99=99
giup mik nhanh nha . mik can gap lam
\(a,x-7\frac{5}{8}=1\frac{1}{4}\)
=> \(x-\frac{61}{8}=\frac{5}{4}\)
=> \(x=\frac{5}{4}+\frac{61}{8}\)
=> \(x=\frac{10}{8}+\frac{61}{8}=\frac{71}{8}=8\frac{7}{8}\)
\(b,x+7\frac{5}{8}=9\frac{1}{4}\)
=> \(x+\frac{43}{5}=\frac{37}{4}\)
=> \(x=\frac{37}{4}-\frac{43}{5}=\frac{13}{20}\)
\(c,\left[x-7\frac{5}{8}\right]:\frac{1}{2}=3\)
=> \(\left[x-\frac{61}{8}\right]=3\cdot\frac{1}{2}\)
=> \(\left[x-\frac{61}{8}\right]=\frac{3}{2}\)
=> \(x-\frac{61}{8}=\frac{3}{2}\)
=> \(x=\frac{3}{2}+\frac{61}{8}=\frac{12}{8}+\frac{61}{8}=\frac{73}{8}=9\frac{1}{8}\)
d, \(\frac{x}{1\cdot3}+\frac{x}{3\cdot5}+\frac{x}{5\cdot7}+...+\frac{x}{97\cdot99}=99\)
=> \(\frac{x}{2}\left[\frac{2}{1\cdot3}+\frac{2}{3\cdot5}+\frac{2}{5\cdot7}+...+\frac{2}{97\cdot99}\right]=99\)
=> \(\frac{x}{2}\left[1-\frac{1}{3}+\frac{1}{3}-\frac{1}{5}+...+\frac{1}{97}-\frac{1}{99}\right]=99\)
=> \(\frac{x}{2}\left[1-\frac{1}{99}\right]=99\)
=> \(\frac{x}{2}\cdot\frac{98}{99}=99\)
=> \(\frac{98x}{198}=99\)
=> 98x = 99 . 198
=> 98x = 19602
=> x = 19602 : 98 = 9801/49
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a) \(x-7\frac{5}{8}=1\frac{1}{4}\)
=> \(x=\frac{5}{4}+\frac{61}{8}\)
=> \(x=\frac{71}{8}\)
b) \(x+7\frac{5}{8}=9\frac{1}{4}\)
=> \(x=\frac{37}{4}-\frac{61}{8}\)
=> \(x=\frac{13}{8}\)
c) \(\left(x-7\frac{5}{8}\right):\frac{1}{2}=3\)
=> \(x-\frac{61}{8}=3.\frac{1}{2}\)
=> \(x-\frac{61}{8}=\frac{3}{2}\)
=> \(x=\frac{3}{2}+\frac{61}{8}\)
=> \(x=\frac{73}{8}\)
d) \(\frac{x}{1.3}+\frac{x}{3.5}+...+\frac{x}{97.99}=99\)
=> \(x.\frac{1}{2}.\left(\frac{2}{1.3}+\frac{2}{3.5}+...+\frac{2}{97.99}\right)=99\)
=> \(\frac{1}{2}x\left(1-\frac{1}{3}+\frac{1}{3}-\frac{1}{5}+....+\frac{1}{97}-\frac{1}{99}\right)=99\)
=> \(x\left(1-\frac{1}{99}\right)=99:\frac{1}{2}\)
=> \(x.\frac{98}{99}=198\)
=> \(x=198:\frac{98}{99}=\frac{9801}{49}\)
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\(b,\text{ }x+7\frac{5}{8}=9\frac{1}{4}\)
\(x=9\frac{1}{4}-\left(7+\frac{5}{8}\right)\)
\(x=9+\frac{1}{4}-7-\frac{5}{8}\)
\(x=\left(9-7\right)+\left(\frac{1}{4}-\frac{5}{8}\right)\)
\(x=2+-\frac{3}{8}\)
\(x=2\frac{-3}{8}\)
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