2 3 3P X X X− + − VỚI X≥0;X≠93 3 9( ) ( )+ + − − +X X X X X2 3 3 3 3= + −P( )( )3 3X X= +( 33)(X 3 3)+ −P X−

2) 2 3 3P x x x− + − với x≥0;x≠93 3 9

( ) ( )

+ + − − +x x x x x2 3 3 3 3= + −P

( )( )

3 3x x= +

(

33

)(

x 3 3

)

+ −P x− . 9x+ + + −P x x x x3 13 3 1 3 3= = = =M Q x x x x x x