1) \(\frac{3x-1}{4}+\frac{2x-3}{3}=\frac{x-1}{2}\) Mc : 12
\(\Leftrightarrow\) \(\frac{3.\left(3x-1\right)}{12}+\frac{4.\left(2x-3\right)}{12}=\frac{6.\left(x-1\right)}{12}\)
\(\Leftrightarrow\) 9x - 3 + 8x - 12 = 6x - 6
\(\Leftrightarrow\) 9x + 8x - 6x = 3 + 12 - 6
\(\Leftrightarrow\) 11x = 9
\(\Leftrightarrow\) x = 0,8
Vậy S = {0,8}
2) \(\frac{x+1}{2}-\frac{x+3}{12}=3-\frac{5-3x}{3}\) Mc : 12
\(\Leftrightarrow\) \(\frac{6.\left(x+1\right)}{12}-\frac{x+3}{12}=\frac{12.3}{12}-\frac{4.\left(5-3x\right)}{12}\)
\(\Leftrightarrow\) 6x + 6 - x + 3 = 36 - 20 - 12x
\(\Leftrightarrow\) 6x - x + 12x = -6 - 3 + 36 - 20
\(\Leftrightarrow\) 17x = 7
\(\Leftrightarrow\) x = \(\frac{7}{17}\)
Vậy S = {\(\frac{7}{17}\)}
3) x - \(\frac{x+1}{3}\) = \(\frac{2x-1}{5}\) Mc : 15
\(\Leftrightarrow\) \(\frac{15.x}{15}-\frac{5.\left(x+1\right)}{15}=\frac{3.\left(2x-1\right)}{15}\)
\(\Leftrightarrow\) 15x - 5x - 5 = 6x - 3
\(\Leftrightarrow\) 15x - 5x - 6x = 5 - 3
\(\Leftrightarrow\) 4x = 2
\(\Leftrightarrow\) x = \(\frac{2}{4}=\frac{1}{2}\)
Vậy S = {\(\frac{1}{2}\)}
4) \(\frac{2x+7}{3}-\frac{x-2}{4}=-2\) Mc : 12
\(\Leftrightarrow\) \(\frac{4.\left(2x+7\right)}{12}-\frac{3.\left(x-2\right)}{12}=\frac{12.\left(-2\right)}{12}\)
\(\Leftrightarrow\) 8x + 28 -3x + 6 = -24
\(\Leftrightarrow\) 8x - 3x = -28 - 6 -24
\(\Leftrightarrow\) 5x = -58
\(\Leftrightarrow\) x = -11,6
Vậy S = {-11,6}
5) \(\frac{2x-3}{4}-\frac{4x-5}{3}=\frac{5-x}{6}\) Mc : 12
\(\Leftrightarrow\) \(\frac{3.\left(2x-3\right)}{12}-\frac{4.\left(4x-5\right)}{12}=\frac{2.\left(5-x\right)}{12}\)
\(\Leftrightarrow\) 6x - 9 - 16x + 20 = 10 - 2x
\(\Leftrightarrow\) 6x - 16x + 2x = 9 - 20 + 10
\(\Leftrightarrow\) -8x = -1
\(\Leftrightarrow\) x = \(\frac{1}{8}\)
Vậy S = {\(\frac{1}{8}\)}
6) \(\frac{12x+1}{4}=\frac{9x+1}{3}-\frac{3-5x}{12}\) Mc : 12
\(\Leftrightarrow\frac{3.\left(12x+1\right)}{12}=\frac{4.\left(9x+1\right)}{12}-\frac{3-5x}{12}\)
\(\Leftrightarrow\) 36x + 3 = 36x + 4 - 3 + 5x
\(\Leftrightarrow\) 36x - 36x - 5x = -3 + 4 - 3
\(\Leftrightarrow\) -5x = -2
\(\Leftrightarrow x=\frac{2}{5}\)
7) \(\frac{x+6}{4}\) - \(\frac{x-2}{6}-\frac{x+1}{3}=0\) Mc : 12
\(\Leftrightarrow\) \(\frac{3.\left(x+6\right)}{12}-\frac{2.\left(x-2\right)}{12}-\frac{4.\left(x+1\right)}{12}=0\)
\(\Leftrightarrow\) 3x + 18 - 2x + 4 - 4x - 4 = 0
\(\Leftrightarrow\) 3x - 2x - 4x = -18 - 4 + 4
\(\Leftrightarrow\) -3x = -18
\(\Leftrightarrow\) x = 6
Vậy S = {6}
8) x\(^2\) - x - 6 = 0
\(\Leftrightarrow\) x\(^2\) + 2x - 3x - 6 = 0
\(\Leftrightarrow\) x.(x + 2) - 3.(x + 2) = 0
\(\Leftrightarrow\) (x - 3).(x + 2) = 0
\(\Leftrightarrow\) x - 3 = 0 hoặc x + 2 = 0
\(\Leftrightarrow\) x = 3 hoặc x = -2
Vậy S = {3; -2}
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