已知a=5,求代數式(a-4)/(a^2-9)除以1/(a-3)乘以(a^2+2a-3)/(a^2-8a+16)的值 已知a=5,求代數式(a-4)/(a^2-9)除以1/(a-3)乘以(a^2+6a+9)/(a^2-8a+16)的值

已知a=5,求代數式(a-4)/(a^2-9)除以1/(a-3)乘以(a^2+2a-3)/(a^2-8a+16)的值 已知a=5,求代數式(a-4)/(a^2-9)除以1/(a-3)乘以(a^2+6a+9)/(a^2-8a+16)的值

(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