1/(x+3)-6/(x的平方-9)-(x-1)/(6-2x)
=1/(x+3)-6/[(x+3)(x-3)]+(x-1)/[2(x-3)]
=[2(x-3)-12+(x-1)(x+3)]/[2(x+3)(x-3)]
=(x²+4x-21)/[2(x+3)(x-3)]
=(x+7)/(2x+6)