Question

先化简(a-1分之2+a^2-1分之a-2)除以a+1分之a,再从-3<a<2中选择一个恰当的整数a代入求值

Answer 1

(a-1分之2+a^2-1分之a-2)除以a+1分之a
=[2/(a-1)+(a-2)/(a+1)(a-1)]÷a/(a+1)
=(2a+2+a-2)/(a+1)(a-1)*(a+1)/a
=3a/(a+1)(a-1)*(a+1)/a
=3/(a-1)
a不等于1
又因为-3<a<2
所以恰当的整数a= -2或 -1或 0
a= -2，原式= -1
a= -1，原式= -3/2
a= 0，原式= -3

Answer 2

解：原式=【2/(a-1)+（a-2)/(a+1）（a-1）】*【(a+1)/a]
=【2(a+1)/(a+1)(a-1)+（a-2)/(a+1）（a-1）】*【(a+1)/a]
=[2(a+1）+（a-2)】/[(a+1)(a-1)]*【(a+1)/a]
=3a/(a+1)(a-1)*【(a+1)/a]
=3/(a-1)
取a=-2原式=3/（-3）=-1

说明：此题中a不能使1，-1,0