a) $2{x^5} + 3{x^2} = 2x \Rightarrow 2{x^5} + 3{x^2} - 2x = 0$

$\left[ {x{{\left( {2x} \right]}^4} + 3{x^2} - 2} \right) = 0$

$2{x^4} + 3{x^2} - 2 = 0$

b) $\left( {{x^2} + 2} \right)\left( {2{x^2} - 1} \right) = 0$

$x =  \pm {\raise0.5ex\hbox{$\scriptstyle 1$}
\kern-0.1em/\kern-0.15em
\lower0.25ex\hbox{$\scriptstyle {\sqrt 2 }$}}$ only

$\left( {{\raise0.5ex\hbox{$\scriptstyle 1$}
\kern-0.1em/\kern-0.15em
\lower0.25ex\hbox{$\scriptstyle {\sqrt 2 }$}},{\raise0.5ex\hbox{$\scriptstyle 2$}
\kern-0.1em/\kern-0.15em
\lower0.25ex\hbox{$\scriptstyle {\sqrt 2 }$}}} \right),\,\left( {{\raise0.5ex\hbox{$\scriptstyle { - 1}$}
\kern-0.1em/\kern-0.15em
\lower0.25ex\hbox{$\scriptstyle {\sqrt 2 ,{\raise0.5ex\hbox{$\scriptstyle { - 2}$}
\kern-0.1em/\kern-0.15em
\lower0.25ex\hbox{$\scriptstyle {\sqrt 2 }$}}}$}}} \right)$