(2,5 : x) + 2 1/5 =2 2/3
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Những câu hỏi liên quan
AN
3
DC
19 tháng 4 2022
= 3/4 + 1/3 = 13/12
5/4 x X = 5/8
X = 5/8 : 5/4
X = 1/2
vậy X = ...
Y
4 tháng 4 2022
\(\dfrac{9}{7}x+\dfrac{5}{7}x=\dfrac{2}{3}\)
\(\Leftrightarrow x\left(\dfrac{9}{7}+\dfrac{5}{7}\right)=\dfrac{2}{3}\)
\(\Leftrightarrow\dfrac{14}{7}x=\dfrac{2}{3}\)
\(\Leftrightarrow2x=\dfrac{2}{3}\)
\(\Leftrightarrow x=\dfrac{2}{3}:2\)
\(\Leftrightarrow x=\dfrac{2}{3}\times\dfrac{1}{2}\)
\(\Leftrightarrow x=\dfrac{2}{6}\)
\(\Leftrightarrow x=\dfrac{1}{3}\)
19 tháng 2 2021
Ta có : \(\dfrac{x}{2}=\dfrac{1-x}{3}\)
\(\Leftrightarrow3x=2\left(1-x\right)\)
\(\Leftrightarrow3x=2-2x\)
\(\Leftrightarrow5x=2\)
\(\Leftrightarrow x=\dfrac{5}{2}\)
Vậy ...
19 tháng 2 2021
Ta có: \(\dfrac{x}{2}=\dfrac{1-x}{3}\)
\(\Leftrightarrow3x=2\left(1-x\right)\)
\(\Leftrightarrow3x=2-2x\)
\(\Leftrightarrow3x+2x=2\)
\(\Leftrightarrow5x=2\)
hay \(x=\dfrac{2}{5}\)
Vậy: \(x=\dfrac{2}{5}\)
VD
20 tháng 3 2022
a,ĐKXĐ:\(\left\{{}\begin{matrix}x\ne\pm1\\x\ne\dfrac{1}{2}\end{matrix}\right.\)
\(A=\left(\dfrac{2}{x+1}-\dfrac{1}{x-1}+\dfrac{5}{x^2-1}\right):\dfrac{2x+1}{x^2-1}\\ =\left(\dfrac{2\left(x-1\right)}{\left(x+1\right)\left(x-1\right)}-\dfrac{x+1}{\left(x+1\right)\left(x-1\right)}+\dfrac{5}{\left(x+1\right)\left(x-1\right)}\right).\dfrac{\left(x-1\right)\left(x+1\right)}{2x+1}\\ =\dfrac{2x-2-x-1+5}{\left(x+1\right)\left(x-1\right)}.\dfrac{\left(x-1\right)\left(x+1\right)}{2x+1}\\ =\dfrac{x+2}{2x+1}\)
\(b,A=3\\ \Leftrightarrow\dfrac{x+2}{2x+1}=3\\ \Leftrightarrow6x+3=x+2\\ \Leftrightarrow5x+1=0\\ \Leftrightarrow x=-\dfrac{1}{5}\left(tm\right)\)
\(c,\dfrac{1}{A}=\dfrac{2x+1}{x+2}=\dfrac{2x+4-3}{x+2}=\dfrac{2\left(x+2\right)-3}{x+2}=2-\dfrac{3}{x+2}\)
Để `1/A` là số nguyên thì `3/(x+2)` nguyên \(\Rightarrow x+2\inƯ\left(3\right)=\left\{-3;-1;1;3\right\}\)
Ta có bảng:
| x+2 | -3 | -1 | 1 | 3 |
| x | -5 | -3 | -1(ktm) | 1(ktm) |
Vậy \(x\in\left\{-5;-3\right\}\)
3 tháng 7 2021
\(\)đặt \(2x^2+y^2+\dfrac{28}{x}+\dfrac{1}{y}=A\)
\(=>A=2x^2+y^2-7x-y+\dfrac{28}{x}+7x+\dfrac{1}{y}+y\)
\(A=2x^2-8x+8+y^2-2y+1+x+y-9+\dfrac{28}{x}+7x+\dfrac{1}{y}+y\)
\(A=2\left(x-2\right)^2+\left(y-1\right)^2+\left(x+y\right)-9+\dfrac{28}{x}+7x+\dfrac{1}{y}+y\)
áp dụng BDT AM-GM\(=>\dfrac{28}{x}+7x+\dfrac{1}{y}+y\ge2\sqrt{28.7}+2\sqrt{1}=30\)
\(=>A\ge30+3-9=24\)
dấu"=" xảy ra<=>x=2,y=1
TH
1
TH
1
HN
2 tháng 4 2022
f(x)=0 \(\Leftrightarrow\) 2x+a2-3=0 \(\Rightarrow\) x=\(\dfrac{3-a^2}{2}\).
a) x=1 \(\Leftrightarrow\) \(\dfrac{3-a^2}{2}\)=1 \(\Rightarrow\) a=\(\pm\)1.
b) x=\(\dfrac{-1}{2}\) \(\Leftrightarrow\) \(\dfrac{3-a^2}{2}\)=\(\dfrac{-1}{2}\) \(\Rightarrow\) a=\(\pm\)2.
30 tháng 1 2021
\(2^x+2^{x+1}+2^{x+2}=960-2^{x+3}\)
\(\Leftrightarrow2^x+2^{x+1}+2^{x+2}+2^{x+3}=960\)
\(\Leftrightarrow2^x\left(1+2+2^2+2^3\right)=960\)
\(\Leftrightarrow2^x.15=960\)
\(\Leftrightarrow2^x=64\)
\(\Leftrightarrow2^x=2^6\Leftrightarrow x=6\)
Vậy...
\(\Leftrightarrow2.5:x=2+\dfrac{2}{3}-2-\dfrac{1}{5}=\dfrac{7}{15}\)
hay \(x=\dfrac{5}{2}:\dfrac{7}{15}=\dfrac{5}{2}\cdot\dfrac{15}{7}=\dfrac{75}{14}\)