1 :Tìm x biết :
—1/8<x/32_<1/16 (với x là số nguyên)
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Vì: |2\(x\) - 1| = |1 - 2\(x\)|
Nên: |2\(x\) - 1| + |1 - 2\(x\)| = 8
⇒ |2\(x\) - 1| + |2\(x\) - 1| = 8
2.|2\(x\) - 1| = 8
|2\(x\) - 1| = 8:2
|2\(x\) - 1| = 4
\(\left[{}\begin{matrix}2x-1=-4\\2x-1=4\end{matrix}\right.\)
\(\left[{}\begin{matrix}2x=-4+1\\2x=4+1\end{matrix}\right.\)
\(\left[{}\begin{matrix}2x=-3\\2x=5\end{matrix}\right.\)
\(\left[{}\begin{matrix}x=-\dfrac{3}{2}\\x=\dfrac{5}{2}\end{matrix}\right.\)
Vậy \(x\) \(\in\){- \(\dfrac{3}{2}\); \(\dfrac{5}{2}\)}
\(\frac{1}{5.8}+\frac{1}{8.11}+\frac{1}{11.14}+...+\frac{1}{x\left(x+3\right)}=\frac{1}{18}\)
\(\Leftrightarrow\frac{1}{3}.\left(\frac{3}{5.8}+\frac{3}{8.11}+\frac{3}{11.14}+.....+\frac{3}{x\left(x+3\right)}\right)=\frac{1}{18}\)
\(\Leftrightarrow\frac{1}{3}.\left(\frac{1}{5}-\frac{1}{8}+\frac{1}{8}-\frac{1}{11}+\frac{1}{11}-\frac{1}{14}+....+\frac{1}{x}-\frac{1}{x+3}\right)=\frac{1}{18}\)
\(\Leftrightarrow\frac{1}{3}.\left(\frac{1}{5}-\frac{1}{x+3}\right)=\frac{1}{18}\Leftrightarrow\frac{1}{5}-\frac{1}{x+3}=\frac{1}{18}:\frac{1}{3}=\frac{1}{6}\)
\(\Leftrightarrow\frac{1}{x+3}=\frac{1}{5}-\frac{1}{6}=\frac{1}{30}\)
<=>x+3=30
<=>x=27
Vậy x=27
1 )
X x 17 - X x 8 = 405
X x ( 17 - 8 ) = 405
X x 9 = 405
X = 405 : 9
X = 45
2 )
2250 : x + 750 = 8
2250 : x = 8 - 750
2250 : x = ...
Có sai đề không bạn ?
ĐK : \(x;y\ne0\)
Ta có : \(\dfrac{1}{x}+\dfrac{1}{y}=\dfrac{1}{8}\)
\(\Leftrightarrow\dfrac{x+y}{xy}=\dfrac{1}{8}\)
\(\Leftrightarrow8.\left(x+y\right)=xy\)
\(\Leftrightarrow xy-8x-8y=0\)
\(\Leftrightarrow\left(xy-8x\right)-\left(8y-64\right)=64\)
\(\Leftrightarrow x.\left(y-8\right)-8.\left(y-8\right)=64\Leftrightarrow\left(x-8\right).\left(y-8\right)=64\)
Do x;y \(\inℤ\) ta có bảng sau
x - 8 | 1 | 2 | 4 | 8 | 16 | 32 | 64 | -1 | -2 | -4 | -8 | -16 | -32 | -64 |
y - 8 | 64 | 32 | 16 | 8 | 4 | 2 | 1 | -64 | -32 | -16 | -8 | -4 | -2 | -1 |
x | 9 | 10 | 12 | 16 | 24 | 40 | 72 | 7 | 6 | 4 | 0(loại) | -8 | -24 | -56 |
y | 72 | 40 | 24 | 16 | 12 | 10 | 9 | -56 | -24 | -8 | 0(loại) | 4 | 6 | 7 |
Vậy (x;y) = (9;72) ; (10 ; 40) ; (12 ; 24) ; (16;16) ; (24;12) ; (7;-56) ; (6;-24) ; (4;-8) và các hoán vị của chúng
Ta thấy \(\left|x+\frac{1}{8}\right|\ge0\forall x;\left|x+\frac{2}{8}\right|\ge0\forall x;\left|x+\frac{5}{8}\right|\ge0\forall x\)
\(\Rightarrow\left|x+\frac{1}{8}\right|+\left|x+\frac{2}{8}\right|+\left|x+\frac{5}{8}\right|\ge0\)
\(\Rightarrow4x\ge0\Rightarrow x\ge0\)
\(\Rightarrow x+\frac{1}{8}+x+\frac{2}{8}+x+\frac{5}{8}=4x\)
\(\Rightarrow3x+1=4x\)
=> x = 1 (t/m)
Vậy x=1
a. \(\dfrac{8}{7}-\dfrac{1}{7}:\left(\dfrac{x}{3}-2\right)=-1\)
\(-\dfrac{1}{7}:\left(\dfrac{x}{3}-2\right)=\dfrac{15}{7}\)
\(\dfrac{x}{3}-2=\dfrac{-1}{15}\)
\(\dfrac{x}{3}=\dfrac{29}{15}\)
\(x=5,8\)
b. \(\dfrac{5}{8}+\dfrac{1}{4}\left(2x-1\right)=\dfrac{5}{4}\)
\(\dfrac{1}{4}\left(2x-1\right)=\dfrac{5}{8}\)
\(2x-1=\dfrac{5}{2}\)
\(2x=\dfrac{7}{2}\)
\(x=\dfrac{7}{4}\)
\(\left(x+\frac{1}{2}\right)+\left(x+\frac{1}{4}\right)+\left(x+\frac{1}{8}\right)+\left(x+\frac{1}{16}\right)=1\)
\(\Leftrightarrow4\text{x}+\frac{1}{2}+\frac{1}{4}+\frac{1}{8}+\frac{1}{16}=1\)
\(\Leftrightarrow4\text{x}+\frac{15}{16}=1\)
\(\Leftrightarrow4\text{x}=1-\frac{15}{16}\)
\(\Leftrightarrow4\text{x}=\frac{1}{16}\)
\(\Leftrightarrow x=\frac{1}{16}:4=\frac{1}{64}\)
(x+1/2)+(x+1/4)+(x+1/8)+(x+16)=1
(x.x.x.x)+(1/2+1/4+1/8+1/16=1
4x+(1/2+1/4+1/8+1/16)=1
4x+(8/16+4/16+2/16+1/16)=1
4x+15/16=1
4x=1-15/16
4x=1/16
x=1/16:4
=>x=1/64
tick cho mk nha bạn
\(\left(x+\frac{1}{2}\right)+\left(x+\frac{1}{4}\right)+\left(x+\frac{1}{8}\right)+\left(x+\frac{1}{16}\right)=1\)
\(\left(x+x+x+x\right)+\left(\frac{1}{2}+\frac{1}{4}+\frac{1}{8}+\frac{1}{16}\right)=1\)
\(4x+\left(1+\frac{1}{2}+\frac{1}{4}+\frac{1}{8}+\frac{1}{16}\right)=1\)
\(4x+\left(1-\frac{1}{2}+\frac{1}{2}-\frac{1}{4}+\frac{1}{4}-\frac{1}{8}+\frac{1}{8}-\frac{1}{16}\right)=1\)
\(4x+\left(1-\frac{1}{16}\right)=1\)
\(4x+\frac{15}{16}=1\)
\(4x=\frac{1}{16}\)
\(\Rightarrow x=\frac{1}{64}\)
\(\left(x+\frac{1}{2}\right)+\left(x+\frac{1}{4}\right)+\left(x+\frac{1}{8}\right)+\left(x+\frac{1}{16}\right)=1\)
\(\left(x+x+x+x\right)+\left(\frac{1}{2}+\frac{1}{4}+\frac{1}{8}+\frac{1}{16}\right)=1\)
\(4x+\frac{15}{16}=1\)
\(4x=\frac{1}{16}\)
\(x=\frac{1}{16}\div4\)
\(x=\frac{1}{64}\)
Vậy ...
\(\frac{-1}{8}< \frac{x}{32}\le\frac{1}{16}\)
\(\Leftrightarrow\frac{-4}{32}< \frac{x}{32}\le\frac{2}{32}\)
\(\Leftrightarrow-4< x\le2\) (khử mẫu)
\(\Leftrightarrow x\in\left\{-3;-2;-1;0;1;2\right\}\)