(a-4)/(a^2-9)除以1/(a-3)乘以(a^2+2a-3)/(a^2-8a+16)
=(a-4)(a-3)(a-1)(a+3)/[(a+3)(a-3)(a-4)²]
=(a-1)/(a-4)
=(5-1)/(5-4)
=4抱歉重答下。。(a-4)/(a^2-9)除以1/(a-3)乘以(a^2+6a+9)/(a^2-8a+16) =(a-4)(a-3)(a+3)²/[(a+3)(a-3)(a-4)²] =(a+3)/(a-4) =(5+3)/(5-4) =8