1 tìm x a, ( x -1 ) ( x + 1/ 2 ) = 0 b , ( 2 x – 1 ) ( x + 2/5 ) = 0 2

Đáp án:

a) $x\in \left \{ 1;\dfrac{1}{2} \right \}$

b) $x\in \left \{ \dfrac{1}{2};-\dfrac{2}{5} \right \}$

Giải thích các bước giải:

a) $(x-1)\left ( x+\dfrac{1}{2} \right )=0$
$\Leftrightarrow \left[ \begin{array}{l}x-1=0\\x+\dfrac{1}{2}=0\end{array} \right.$
$\Leftrightarrow \left[ \begin{array}{l}x=1\\x=-\dfrac{1}{2}\end{array} \right.$
Vậy $x\in \left \{ 1;\dfrac{1}{2} \right \}$
b) $(2x-1)\left ( x+\dfrac{2}{5} \right )=0$
$\Leftrightarrow \left[ \begin{array}{l}2x-1=0\\x+\dfrac{2}{5}=0\end{array} \right.$
$\Leftrightarrow \left[ \begin{array}{l}x=\dfrac{1}{2}\\x=-\dfrac{2}{5}\end{array} \right.$
Vậy $x\in \left \{ \dfrac{1}{2};-\dfrac{2}{5} \right \}$