Tìm x, biết: ( x - 2/7)( x + 3/4) = 0
Tìm x, biết: \(\left( {x - \frac{2}{7}} \right)\left( {x + \frac{3}{4}} \right) = 0\).
Lời giải
Ta có \(\left( {x - \frac{2}{7}} \right)\left( {x + \frac{3}{4}} \right) = 0\).
\( \Leftrightarrow \left[ \begin{array}{l}x - \frac{2}{7} = 0\\x + \frac{3}{4} = 0\end{array} \right.\)
\( \Leftrightarrow \left[ \begin{array}{l}x = \frac{2}{7}\\x = - \frac{3}{4}\end{array} \right.\)
Vậy \(x \in \left\{ {\frac{2}{7}; - \frac{3}{4}} \right\}\).