`a,(2x-x^2)(2x^2 -3x-2)=0`

`<=>x(2-x)(2x^2 -4x+x-2)=0`

`<=>x(x-2)[2x(x-2)+(x-2)]=0`

`<=>x(2x+1)(x-2)^2 =0`

`<=>`$\left[ \begin{array}{l}x=0\\x=2\\x=\dfrac{-1}{2}\end{array} \right.$ 

`=>A={0;2;-1/2}`

`b, 2 <x^2 <30`

`=>x^2 in {4;9;16;25}`

`=>x in {+- 2 ; +- 3 ; +- 4 ; +- 5}`

Mà `x in N => x in {2;3;4;5}`

 `=> B= {2;3;4;5}`

`c,(2x^2 -5x+3)(x^2 -4x+3)=0`

`<=>(2x^2 -2x-3x+3)(x^2 -x-3x+3)=0`

`<=>[2x(x-1)-3(x-1)][x(x-1)-3(x-1)]=0`

`<=>(2x-3)(x-3)(x-1)^2 =0`

`<=>`$\left[ \begin{array}{l}x=\dfrac{3}{2}\\x=3\\x=1\end{array} \right.$ 

Mà `x in Z =>x in {1;3}`

`=>C={1;3}`

`d, 3+x<4+2x`

`<=>2x+4-x-3 >0`

`<=>x+1>0`

`<=>x > -1`

Mà `x in N =>x  in {0;1;2;...}`

`=>D={0;1;2;....}`

`e,5x+3<4x-1`

`<=>5x+3-4x+1<0`

`<=>x+4 <0`

`<=>x < -4`

Mà `x in N => x in` $\varnothing$

`=>` $D = \varnothing$