Question

先化简后求值a²-5a+6分之a²-1除以a-3分之a²+a-2减去a²-4分之a+3 其中a=-3

Answer 1

∵a=-3，∴a²-4分之a+3=0
a²-5a+6分之a²-1除以a-3分之a²+a-2减去a²-4分之a+3
=(a+1)(a-1)/[(a-2)(a-3)]÷[(a+2)(a-1)/(a-3)]
=(a+1)(a-1)/[(a-2)(a-3)]*(a-3)/[(a+2)(a-1)]
=(a+1)/[(a-2)(a+2)]
=-2/[(-5)*(-1)]
=-2/5

Answer 2

原式=(a+1)(a-1)/(a-2)(a-3)×(a-3)/a(a-1)-(a+3)/(a+2)(a-2)
=(a+1)/a(a-2)-(a+3)/(a+2)(a-2)
=(a²+3a+2-a²-3a)/a(a+2)(a-2)
=2/a(a+2)(a-2)
=2/(-15)
=-2/15

追问

错了

追答

原式=(a+1)(a-1)/(a-2)(a-3)×(a-3)/(a+2)(a-1)-(a+3)/(a+2)(a-2)
=(a+1)/(a-2)(a+2)-(a+3)/(a+2)(a-2)
=-2/(a+2)(a-2)
=-2/(a²-4)
=-2/(9-4)
=-2/5