x≠3因为：x-3在分母上,所以：x-3≠0,即：x≠3(x²-9)/(x-3)²=(x+3)/(x-3)(x+3)(x-3)/(x-3)²=(x+3)/(x-3)(x+3)/(x-3)=(x+3)/(x-3)1=1可见,x≠3时,所给分式变成了一个恒等式.故,所给分式成立的条件是：...