Đang nghĩ câu $10)$ .
$1) 3x+5=2x-4$
$⇔ 5+4= 2x-3x$
$⇔ -x = 9$
$⇔ x = -9$
Vậy $x=-9$
$2) x-7-(2x+1)=5$
$⇔ x-7-2x - 1 =5$
$⇔ x - 2x = 5+1+7$
$⇔ -x = 13$
$⇔ x = -13$
Vậy $x=-13$
$3)(2x-7)-(7x+5)=6$
$⇔ 2x - 7 - 7x - 5 = 6$
$⇔ 2x - 7x = 6+5+7$
$⇔ -5x = 18$
$⇔ x = -18/5$
Vậy $x = - 18/5$
$4) (x+3)-(2x+1)=5$
$⇔ x+3 - 2x - 1 = 5$
$⇔ x - 2x = 5+1 - 3$
$⇔ -x = 3$
$⇔ x = -3$
Vậy $x=-3$
$5) $x+2/3-x/2=x$
$⇔ 2/3 - x/2 = x -x$
$⇔ 2/3 - x/2 = 0$
$⇔ x/2 = 2/3$
$⇔ x = 4/3$
Vậy $x=4/3$
$6) x+7/2-x=1/2$
$⇔ 7/2 = 1/2$ ($KTM$)
Vậy $x$ $∈$ $∅$.
$7) (x-5)(x+3)=0$
$⇒$ \(\left[ \begin{array}{l}x-5=0\\x+3=0\end{array} \right.\)
$⇔$ \(\left[ \begin{array}{l}x=5\\x=-3\end{array} \right.\)
Vậy $x$ $∈$ {$-3;5$}
$8) (x-3)(x+2)=0$
$⇒$ \(\left[ \begin{array}{l}x-3=0\\x+2=0\end{array} \right.\)
$⇔$ \(\left[ \begin{array}{l}x=3\\x=-2\end{array} \right.\)
Vậy $x$ $∈$ {$-2;3$}
$9)x+1/1+1/2x=1/2$
$⇔ x + 1 + 1/2x = 1/2$
$⇔ x+1/2.x = 1/2 - 1$
$⇔ x/1 + x/2 = -1/2$
$⇔ 2x/2 + x/2 = -1/2$
$⇔ 3x = -1$
$⇔ x = -1/3$
Vậy $x=-1/3$
