tìm x,biết
2.4:[-1/2-x]=8/5
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NA
2
4 tháng 5 2018
\(\frac{1}{2\cdot4}+\frac{1}{4\cdot6}+...+\frac{1}{\left(2x-2\right)\cdot2x}=\frac{1}{8}\)
\(\Rightarrow\frac{2}{2\cdot4}+\frac{2}{4\cdot6}+...+\frac{2}{\left(2x-2\right)\cdot2x}=\frac{2}{8}\)
\(\Rightarrow\frac{1}{2}-\frac{1}{4}+\frac{1}{4}-\frac{1}{6}+...+\frac{1}{2x-2}-\frac{1}{2x}=\frac{1}{4}\)
\(\Rightarrow\frac{1}{2}-\frac{1}{2x}=\frac{1}{4}\)
\(\Rightarrow\frac{1}{2x}=\frac{1}{2}-\frac{1}{4}\)
\(\Rightarrow\frac{1}{2x}=\frac{1}{4}\)
\(\Rightarrow2x=4\)
\(\Rightarrow x=2\)
22 tháng 4 2018
1/(2.4) + 1/(4.6) + … + 1/[(2x – 2).2x] = 1/8
suy ra 2/(2.4) + 2/(4.6) + ...+ 2/[(2x - 2).2x] = 2/8
suy ra 1-1/4+1/4-1/6+...+1/(2x-2) - 1/2x = 2/8
suy ra 1 - 1/2x = 2/8
suy ra 1/2x = 1 - 2/8
suy ra 1/2x = 6/8 = 3/4
suy ra 1.4 = 2.x.3
suy ra 4 = 6x
suy ra x thuộc rỗng
Vậy x thuộc rỗng
k cho mình nha. Chúc bạn học tốt!
19 tháng 8 2018
a. 20 + 8.(x + 3) = 52 . 4
8.(x + 3) = 100 - 20
x + 3 = 80 : 8
x = 10 - 3
x = 7
b. 120 + |x| = 150
|x| = 150 - 120
|x| = 30
x = + 30
19 tháng 8 2018
a) 20 + 8(x + 3) = 52 . 4
20 + 8(x + 3) = 100
8(X + 3) = 100 - 20
8(x + 3) = 80
x + 3 = 80 : 8
x + 3 = 10
x = 10 - 3
x = 7
b) 120 + |x| = 150
|x| = 150 - 120
|x| = 30
=> \(\orbr{\begin{cases}x=30\\x=-30\end{cases}}\)
MN
2
5 tháng 2 2018
\(\left(9!-8!\right).7!.x=1^2.2^2.3^2.4^2.....8^2\)
\(\Leftrightarrow\)\(8!\left(9-1\right).7!.x=\left(1.2.3.4.....8\right).\left(1.2.3.4.....8\right)\)
\(\Leftrightarrow\)\(8!.8.7!.x=8!.8!\)
\(\Leftrightarrow\)\(8!.8!.x=8!.8!\)
\(\Leftrightarrow\)\(x=\frac{8!.8!}{8!.8!}\)
\(\Leftrightarrow\)\(x=1\)
Vậy \(x=1\)
5 tháng 2 2018
\(\left(9!-8!\right).7!.x=1^2.2^2.3^2.4^2.....8^2\)
\(\Leftrightarrow\)\(8!\left(9-1\right).7!.x=\left(1.2.3.4.....16\right).\left(1.2.3.4.....16\right)\)
\(\Leftrightarrow\)\(8!.8.7!.x=8!.8!\)
\(\Leftrightarrow\)\(8!.8!.x=8!.8!\)
\(\Leftrightarrow\)\(x=\frac{8!.8!}{8!.8!}\)
\(\Leftrightarrow\)\(x=1\)
Vậy \(x=1\)
Vậy
KN
1 tháng 5 2019
\(\frac{1}{2.4}+\frac{1}{4.6}+...+\frac{1}{\left(2x-2\right).2x}=\frac{1}{8}\)
\(\Rightarrow\frac{1}{2}\left(\frac{2}{2.4}+\frac{2}{4.6}+...+\frac{2}{\left(2x-2\right).2x}\right)=\frac{1}{8}\)
\(\Rightarrow\frac{1}{2}-\frac{1}{4}+\frac{1}{4}-\frac{1}{6}+...+\frac{1}{2x-2}-\frac{1}{2x}=\frac{1}{8}:\frac{1}{2}\)
\(\Rightarrow\frac{1}{2}-\frac{1}{2x}=\frac{1}{4}\)
\(\Rightarrow\frac{1}{2x}=\frac{1}{2}-\frac{1}{4}=\frac{1}{4}\)
\(\Leftrightarrow2x=4\)
\(\Leftrightarrow x=2\)
26 tháng 6 2019
TL:
\(\frac{1}{2}\left(\frac{2}{2.4}+\frac{2}{4.6}+....+\frac{2}{\left(2x-2\right)2x}\right)=\frac{1}{8}\)
\(\frac{1}{2}-\frac{1}{4x}=\frac{1}{8}\)
\(\frac{1}{4x}=\frac{3}{8}\)
=>x=2/3
hc tốt
19 tháng 10 2016
\(a,60-3.\left(x-2\right)=51\)
\(3.\left(x-2\right)=60-51\)
\(3.\left(x-2\right)=9\)
c \(x-2=9:3\)
\(x-2=3\)
\(x=3+2\)
\(x=5\)
\(b,541+\left(218-x\right)=725\)
\(218-x=725-541\)
\(218-x=184\)
\(x=218-184\)
\(x=34\)
\(c,3.\left(5x-13\right)=3^4\)
\(3.\left(5x-13\right)=81\)
\(5x-13=81:3\)
\(5x-13=27\)
\(5x=27+13\)
\(5x=40\)
\(x=8\)
19 tháng 10 2016
\(d,\left(2x-7\right)-\left(x+135\right)=0\)
\(2x-7-x-135=0\)
\(x-142=0\)
\(x=0+142\)
\(x=142\)
LT
2
30 tháng 4 2018
\(\frac{1}{2.4}+\frac{1}{4.6}+...+\frac{1}{\left(2x-2\right).2x}\)= \(\frac{1}{8}\)
\(\frac{1}{2}.\left(\frac{2}{2.4}+\frac{2}{4.6}+...+\frac{2}{\left(2x-2\right).2x}\right)\)= \(\frac{1}{8}\)
\(\frac{1}{2}.\left(\frac{1}{2}-\frac{1}{2x}\right)\)= \(\frac{1}{8}\)
=> \(\frac{1}{2}-\frac{1}{2x}\)= \(\frac{1}{4}\)
=> 1/2x = 1/4
=> 2x = 4
x = 4 : 2
x = 2
30 tháng 4 2018
\(\frac{1}{2.4}+\frac{1}{4.6}+...+\frac{1}{\left(2x-2\right)2x}=\frac{1}{8}\)
\(\Rightarrow\frac{1}{2}\left(\frac{1}{2}-\frac{1}{4}+\frac{1}{4}-\frac{1}{6}+...+\frac{1}{2x-2}-\frac{1}{2x}\right)=\frac{1}{8}\)
\(\Rightarrow\frac{1}{2}-\frac{1}{2x}=\frac{1}{8}.2=\frac{1}{4}\)
\(\Rightarrow\frac{1}{2x}=\frac{1}{2}-\frac{1}{4}=\frac{1}{4}\)
\(\Rightarrow2x=4\Leftrightarrow x=2\)
HM
0
\(2.4:\left(\frac{-1}{2}-x\right)=\frac{8}{5}\)
\(8:\left(\frac{-1}{2}-x\right)=\frac{8}{5}\)
\(\frac{-1}{2}-x=5\)
\(x=\frac{-55}{10}\)
Vậy \(x=\frac{-55}{10}\)
\(2.4:\left(-\frac{1}{2}-x\right)=\frac{8}{5}\)
\(8:\left(-\frac{1}{2}-x\right)=\frac{8}{5}\)
\(-\frac{1}{2}-x=8:\frac{8}{5}\)
\(-\frac{1}{2}-x=\frac{1}{5}\)
\(x=-\frac{1}{2}-\frac{1}{5}\)
\(x=-\frac{7}{10}\)