是9x-x³
原式=(x²+3x+9)/(x-3)(x²+3x+9)-6x/x(x-3)(x+3)-(x-1)/2(x+3)
=1/(x-3)-6/(x-3)(x+3)-(x-1)/2(x+3)
=(2x+6-12-x²+4x-3)/2(x+3)(x-3)
=-(x²-6x+9)/2(x+3)(x-3)
=-(x-3)²/2(x+3)(x-3)
=(3-x)/(2x+6)确实是9x-x²不可能的别问了追求的是一种真理不信就算了