$2x^{4}$ - $5x^{2}$ + 3 = 0
=>$2x^{4}$ - $2x^{2}$ - $3x^{2}$ + 3=0
=>($2x^{4}$ - $2x^{2}$)-($3x^{2}$ - 3)=0
=>$2x^{2}$($x^{2}$-1)-3($x^{2}$-1)=0
=>($2x^{2}$-3)($x^{2}$-1)=0
=>\(\left[ \begin{array}{l}2x^{2}-3=0\\x^{2}-1=0\end{array} \right.\)
=>\(\left[ \begin{array}{l}2x^{2}=3\\x^{2}=1\end{array} \right.\)
=>\(\left[ \begin{array}{l}x^{2}=\frac{3}{2}\\x=\pm1\end{array} \right.\)
vậy....