Ta có
\(\eqalign{& 2{x^2} + 5x = 0 \Leftrightarrow x\left( {2x + 5} \right) = 0 \cr & \Leftrightarrow \left[ \matrix{x = 0 \hfill \cr 2x + 5 = 0 \hfill \cr} \right. \Leftrightarrow \left[ \matrix{x = 0 \hfill \cr x =\dfrac{-5}{2} \hfill \cr} \right. \cr} \)
Vậy phương trình có hai nghiệm
\({x_1} = 0;\,\,{x_2} = \displaystyle {{ - 5} \over 2}\)
