答：1/(x+2)-1/(x-8)=1/(x+3)-1/(x+9)
[(x-8)-(x+2)]/[(x+2)(x-8)]=[(x+9)-(x+3)]/[(x+3)(x+9)]
-10/(x^2-6x-16)=6/(x^2+12x+27)
-10x^2-120x-270=6x^2-36x-96
16x^2+84x+174=0
8x^2+42x+87=0
判别式=42^2-4*8*87=-1020