Tìm x : 10-2x/6 = 27/5-x
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\(\frac{2x-10}{6}=\frac{-27}{5-x}\)
\(\frac{2\left(x-5\right)}{6}=\frac{27}{x-5}\)
\(2\left(x-5\right)^2=27\times6\)
\(2x^2-20x+50-162=0\)
\(2x^2-20x-112=0\)
\(x^2-10x-56=0\)
\(x^2-14x+4x-56=0\)
\(\left(x-14\right)\left(x+4\right)=0\)
\(\Leftrightarrow\orbr{\begin{cases}x-14=0\\x+4=0\end{cases}}\Leftrightarrow\orbr{\begin{cases}x=14\\x=-4\end{cases}}\)
KL .....
XIN TIICK
\(1\)) \(5-\left(10-x\right)=7\)
\(10-x=5-7\)
\(10-x=-2\)
\(x=10-\left(-2\right)\)
\(x=12\)
\(2\)) \(-32-\left(x-5\right)=0\)
\(x-5=-32-0\)
\(x-5=-32\)
\(x=-32+5\)
\(x=-27\)
\(\frac{10-2x}{6}=\frac{27}{5-x}\)
\(\Rightarrow\frac{2.\left(5-x\right)}{6}=\frac{27}{5-x}\)
\(\Rightarrow\frac{5-x}{3}=\frac{27}{5-x}\)
\(\Rightarrow\left(5-x\right).\left(5-x\right)=3.27\)
\(\Rightarrow\left(5-x\right)^2=81\)
\(\Rightarrow\left(5-x\right)^2=9^2\)
\(\Rightarrow5-x=\pm9\)
\(\Rightarrow\orbr{\begin{cases}5-x=9\\5-x=-9\end{cases}}\)
\(\Rightarrow\orbr{\begin{cases}x=-4\\x=14\end{cases}}\)
Lời giải:
a. $121-3(x-5)=6$
$3(x-5)=121-6=115$
$x-5=115:3=\frac{115}{3}$
$x=\frac{115}{3}+5=\frac{130}{3}$
b.
$2x-138=2^3.3^2=72$
$2x=72+138=210$
$x=210:2=105$
c.
$x-3\vdots 7$
$\Rightarrow x-3\in\left\{0;7;14;21;28;35;42;49; 56;...\right\}$
Mà $10< x< 50$ nên $x\in\left\{14;21;28;35;42;49\right\}$
d.
$27\vdots x+1$
$\Rightarrow x+1\in\left\{\pm 1; \pm 3; \pm 9; \pm 27\right\}$
$\Rightarrow x\in\left\{0; -2; -4; 2; 8; -10; 26; -28\right\}$
a ) 121-3.(x - 5 ) = 6
3.(x-5) = 121 -6
3. (x-5)=115
x-5 = 115:3
x-5=35
x=35+5
x = 40
b) 2x - 138 = 2'3. 3'2
2x -138=8.9
2x-138=72
2x=72+138
2x=210
x=210:2
x=105
c) theo bài ra : x-3 ∈ B(7)
ta có B(7)=(0,7,14,21,28,35,49,56,...)
=) x-3 ∈ ( 0,7,14,21,28,35,49,56,...)
=) x ∈( 3 , 10,17,24,31,38,42,58,..)
mà 10 <x<50 nên x ∈ ( 17 , 24 ,31,38,42 )
vậy x ∈(17,24,31,38,42)
=> (10 - 2x)(5 - x) = 27.6
=> 10(5 - x) - 2x(5 - x) = 162
=> 50 - 10x - 10x + 2x2 = 162
=> 50 - 20x + 2x2 = 162
=> 2(x2 - 10x +25) = 162
=> x2 - 10x + 25 = 81
=> x2 - 2.x.5 + 52 = 81
=> (x - 5)2 = 81
=> (x - 5)2 = (\(\pm\)9)2
+) x + 5 = 9 => x = 4
+) x + 5 = -9 => x = -14
Tìm x
\(\frac{10-2x}{6}=\frac{27}{5-x}\Leftrightarrow\left(10-2x\right)\left(5-x\right)=6.27\)
\(\Leftrightarrow10\left(5-x\right)-2x\left(5-x\right)=162\)
\(\Leftrightarrow50-10x-10x+2x^2=162\)
\(\Leftrightarrow50-20x+2x^2=126\)
\(\Leftrightarrow2\left(x^2-10x+25\right)=162\)
\(\Leftrightarrow\left(x-5\right)^2=162:2\)
\(\Leftrightarrow\left(x-5\right)^2=81\)
\(\Leftrightarrow\hept{\begin{cases}x-5=9\\x-5=-9\end{cases}}\)\(\Leftrightarrow\hept{\begin{cases}x=4\\x=-14\end{cases}}\)
a, \(\frac{\left(5-2x\right)}{3}=\frac{\left(4x-1\right)}{-5}\)
\(\Leftrightarrow-5(5-2x)=3\left(4x-1\right)\)
\(\Leftrightarrow10x-25=12x-3\)
\(\Leftrightarrow10x-12x=25-3\)
\(\Leftrightarrow-2x=22\)
\(\Leftrightarrow x=-11\)
b, \(\frac{\left(12-3x\right)}{32}=\frac{6}{\left(4-x\right)}\)
\(\Leftrightarrow\frac{3\left(4-x\right)}{32}=\frac{6}{\left(4-x\right)}\)
\(\Leftrightarrow3(4-x)\left(4-x\right)=32.6\)
\(\Leftrightarrow(4-x)\left(4-x\right)=32.2\)
\(\Leftrightarrow(4-x)^2=64\)
\(\Leftrightarrow\orbr{\begin{cases}4-x=8\\4-x=-8\end{cases}}\)
\(\Leftrightarrow\orbr{\begin{cases}x=-4\\x=12\end{cases}}\)
c, \(\frac{\left(10-2x\right)}{6}=\frac{27}{\left(5-x\right)}\)
\(\Leftrightarrow\frac{2\left(5-x\right)}{6}=\frac{27}{\left(5-x\right)}\)
\(\Leftrightarrow2(5-x)\left(5-x\right)=27.6\)
\(\Leftrightarrow(5-x)\left(5-x\right)=27.3\)
\(\Leftrightarrow(5-x)^2=81\)
\(\Leftrightarrow\orbr{\begin{cases}5-x=9\\5-x=-9\end{cases}}\)
\(\Leftrightarrow\orbr{\begin{cases}x=-4\\x=14\end{cases}}\)
a, \(\frac{5-2x}{3}=\frac{4x-1}{-5}\Leftrightarrow-25+10x=12x-3\Leftrightarrow-22-2x=0\Leftrightarrow x=-11\)
b, \(\frac{12-3x}{32}=\frac{6}{4-x}\Leftrightarrow\frac{12-3x}{32}=\frac{18}{12-3x}\)
\(\Leftrightarrow\left(12-3x\right)^2=576\Leftrightarrow12-3x=\pm2\)\(\Leftrightarrow\orbr{\begin{cases}x=\frac{10}{3}\\x=\frac{14}{3}\end{cases}}\)
c, \(\frac{10-2x}{6}=\frac{27}{5-x}\Leftrightarrow\frac{10-2x}{6}=\frac{54}{10-2x}\)
\(\Leftrightarrow\left(10-2x\right)^2=324\Leftrightarrow10-2x=\pm18\)\(\Leftrightarrow\orbr{\begin{cases}x=14\\x=-4\end{cases}}\)
a) \(5-\frac{2x}{3}=4x-\frac{1}{-5}\)
\(\frac{75-10x}{15}=\frac{60x+3}{15}\)
75 - 10x = 60x +3
72 = 70x
\(\frac{72}{70}\) = x
x =\(\frac{36}{35}\)
Vậy x = \(\frac{36}{35}\)
b) \(2x-\frac{10}{6}=\frac{-27}{5}-x\)
\(2x-\frac{5}{3}=\frac{-27}{5}-x\)
\(\frac{30x-25}{15}=\frac{-81-15}{15}\)
30x =-96+25
30x =-71
x= -71/30
Vậy x= -71/30
c) \(13x-\frac{2}{2x}+5=\frac{76}{17}\)
13x - 1/x +5 = 76/17
\(\frac{221x-17+85}{17x}=\frac{76x}{17x}\)
221x +68 = 76x
221x-76x =-68
145x =-68
x =\(\frac{-68}{145}\)
Vậy .........
\(10-\frac{2x}{6}=\frac{27}{5}-x\)
\(-\frac{2x}{6}+x=\frac{27}{5}-10\)
\(-\frac{2x}{6}+\frac{6x}{6}=-\frac{23}{5}\)
\(\frac{2}{3}x=\frac{-23}{5}\)
\(x=\frac{-23}{5}:\frac{2}{3}\)
\(x=\frac{-69}{10}\)
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