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c) pt <=> \(x-\frac{21}{5}=\frac{23}{7}< =>x=\frac{23}{7}+\frac{21}{5}=\frac{262}{35}\)
vậy x = \(\frac{262}{35}\)
d) \(x-\frac{3}{4}=\frac{51}{8}< =>x=\frac{51}{8}+\frac{3}{4}=\frac{57}{8}\)
vậy x = \(\frac{57}{8}\)
e) pt <=> \(\frac{7}{8}:x=\frac{7}{2}< =>\frac{7}{8}.\frac{1}{x}=\frac{7}{2}< =>\frac{7}{8x}=\frac{7}{2}< =>56x=14< =>x=\frac{14}{56}=\frac{1}{4}\)
vậy x = \(\frac{1}{4}\)
a) pt <=> \(x+\frac{11}{4}=\frac{17}{3}< =>x=\frac{17}{3}-\frac{11}{4}=\frac{35}{12}\)
vậy x = \(\frac{35}{12}\)
b) pt <=> \(\frac{x.7}{2}=\frac{19}{4}< =>x=\frac{19.2}{4.7}=\frac{38}{28}=\frac{19}{14}\)
vậy x = \(\frac{19}{14}\)
Dạng 3 :
a) 3x - 10 = 2x + 13
=> 3x - 2x = 13 - 10
=> x = 3
b) x + 12 = -5 - x
=> x + x = -5 - 12
=> 2x = -17
=> x = -8,5
c) x + 5 = 10 - x
=> x + x = 10 - 5
=> 2x = 5
=> x = 2,5
d) 6x + 23 = 2x - 12
=> 2x - 6x = 23 + 12
=> -4x = 35
=> x = -8,75
e) 12 - x = x + 1
=> x + x = 12 - 1
=> 2x = 11
=> x = 5,5
f) 14 + 4x = 3x + 20
=> 4x - 3x = 20 - 14
=> x = 6
a) \(\frac{5}{6}=\frac{x-1}{x}\)
\(5x=6x-6\)
\(6x-5x=6\)
\(x=6\)
các câu còn lại lm tương tự
hok tốt!!
b) \(\frac{1}{2}=\frac{x+1}{3x}\)
\(\Rightarrow1.3x=2.\left(x+1\right)\)
\(3x=2x+2\)
\(3x-2x=2\)
\(x=2\)
Vậy x=2
các câu khác bạn làm tương tự
a) (5x - 1) : 3 + 1 = 4
=> (5x - 1) : 3 = 3
=> (5x - 1) = 9
=> 5x - 1 = 9
=> 5x = 10
=> x = 2
b) 54 : (16 - x) - 1=5
=> 54:(16-x) = 6
=> 16-x = 9
=> x = 7
Bài 1
a) \(\frac{5}{6}=\frac{x-1}{x}\)
<=> 5x=6x-6
<=> 5x-6x=-6
<=> -11x=-6
<=> \(x=\frac{6}{11}\)
b)c)d) nhân chéo làm tương tự
a) \(3^{x+1}=729\)\(\Leftrightarrow3.3^x=729\Rightarrow3^x=243\Rightarrow3^x=3^5\Rightarrow x=5\)
b) \(2^x+2^{x+1}+2^{x+3}=704\Rightarrow2^x+2^x.2+2^x.2^3=704\Rightarrow2^x\left(1+2+8\right)=704\)
\(\Rightarrow2^x.11=704\Rightarrow2^x=64\Rightarrow2^x=2^5\Rightarrow x=5\)
a) Ta có: \(\frac{x+1}{3}=\frac{2}{6}\)
⇔\(x=\frac{2\cdot3}{6}-1=\frac{6}{6}-1=1-1=0\)
Vậy: x=0
b) Ta có: \(\frac{x-1}{4}=\frac{1}{-2}\)
⇔\(x=\frac{1\cdot4}{-2}+1=\frac{4}{-2}+1=-1\)
Vậy: x=-1
c) Ta có: \(\frac{-1}{6}=\frac{3}{2x}\)
⇔\(2x=\frac{3\cdot6}{-1}=-18\)
hay x=-9
Vậy: x=-9
d) Ta có: \(\frac{x+1}{3}=\frac{3}{x+1}\)
⇔\(\left(x+1\right)^2=9\)
\(\Leftrightarrow\left[{}\begin{matrix}x+1=3\\x+1=-3\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=2\\x=-4\end{matrix}\right.\)
Vậy: x∈{2;-4}
e) Ta có: \(\frac{4}{5}=\frac{-12}{9-x}\)
⇔\(9-x=\frac{-12\cdot5}{4}=-15\)
hay x=24
Vậy: x=24
f) Ta có: \(\frac{x-1}{-4}=\frac{-4}{x-1}\)
⇔\(\left(x-1\right)^2=16\)
\(\Leftrightarrow\left[{}\begin{matrix}x-1=4\\x-1=-4\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=5\\x=-3\end{matrix}\right.\)
Vậy: x∈{5;-3}
g) Ta có: \(\frac{5-x}{2}=\frac{2}{5-x}\)
⇔\(\left(5-x\right)^2=4\)
⇔\(\left[{}\begin{matrix}5-x=2\\5-x=-2\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=3\\x=7\end{matrix}\right.\)
Vậy: x∈{3;7}
h) Ta có: \(\frac{4-x}{-5}=\frac{-5}{4-x}\)
⇔\(\left(4-x\right)^2=25\)
⇔\(\left[{}\begin{matrix}4-x=5\\4-x=-5\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=-1\\x=9\end{matrix}\right.\)
Vậy: x∈{-1;9}
a) x = 3
b) x = 3
c) x = 1
d) x = 23