a,f(x)=x²-4
=>(x-2)(x+2)=0
<=>$\left \{ {{x-2=0} \atop {x+2=0}} \right.$
<=>$\frac{x=2}{x=-2}$
b,g(x)= 2x²-x
=>x.(2x-1)
<=>$\left \{ {{x=0} \atop {2x-1=0}} \right.$
<=>x=0 hoặc x=$\frac{1}{2}$
c, h(x)= x-$\frac{1}{2x^2}$
=>2x^3-1=0
=>2x^3=1
=>x^3=$\frac{1}{2}$
d,P(x)= (x-1)(2x+3)
<=>$\left \{ {{x-1=0} \atop {2x+3=0}} \right.$
<=>x=1 hoặc x=$\frac{-3}{2}$