Tìm x, biết 2x^2 + 5x - 3 = 0
Giải thích
PT \( \Leftrightarrow 2{x^2} + 6x - x - 3 = 0 \Leftrightarrow 2x\left( {x + 3} \right) - \left( {x + 3} \right) = 0\)
\( \Leftrightarrow \left( {x + 3} \right)\left( {2x - 1} \right) = 0 \Leftrightarrow \left[ {\begin{array}{*{20}{c}}{x + 3 = 0}\\{2x - 1 = 0}\end{array}} \right. \Leftrightarrow \left[ {\begin{array}{*{20}{c}}{x = - 3}\\{x = \frac{1}{2}}\end{array}} \right.\).