Question

先化简，再求值：A-3/2A-4除以(5/(a-2)-a-2),其中a=1

Answer 1

不用化简,a=1直接代入计算也方便.
(a-3)/(2a-4)除以(5/(a-2)-a-2)
= (1-3)/(2-4)÷[5/(1-2) -1-2]
=1÷(-5-3)
= -1/8

追问

帮我化一下，我的老师狡猾的，要过程

追答

(a-3)/(2a-4)除以(5/(a-2)-a-2)

=(a-3)/[2(a-2)]÷[(5-a²+4)/(a-2)]

=(a-3)/2 × 1/[(3-a)(3+a)]
=-1/(6+2a)
=-1/(6+2)
=-1/8