`a)` ĐK : ` x ne +-3;2`
`P=((3+x)/(3-x)-(3-x)/(3+x)+(4x^2)/(x^2-9)):((2x+1)/(x+3)-1)`
`=(((3+x)^2-(3-x)^2)/(9-x^2)+(4x^2)/(x^2-9)) : (2x+1-(x+3))/(x+3)`
`=((9+6x+x^2-9+6x-x^2)/(9-x^2)+(4x^2)/(x^2-9)):(2x+1-x-3)/(x+3)`
`=((12x)/(9-x^2)+(4x^2)/(x^2-9)):(x-2)/(x+3)`
`=(-12x+4x^2)/(x^2-9) . (x+3)/(x-2)`
`=(4x(x-3))/((x-3)(x+3)).(x+3)/(x-2)`
`=(4x)/(x-2)`
Vậy với `x ne +-3;2` thì `P=(4x)/(x-2)`
`b)`
`2x^2-5x+2=0`
`<=> 2x^2-4x-x+2=0`
`<=> 2x(x-2)-(x-2)=0`
`<=> (2x-1)(x-2)=0`
`<=> [(2x-1=0),(x-2=0):} <=>` \(\left[ \begin{array}{l}x=\dfrac{1}{2} \ \rm (tm)\\x=2\ \rm (ktm)\end{array} \right.\)
Với `x=1/2` thì $P=\dfrac{4 . \dfrac{1}{2}}{\dfrac{1}{2}-2}=\dfrac{2}{-\dfrac{3}{2}}=-\dfrac{4}{3}$
