[a^2-4/(a-3)(a+2)+(a+2)/a-3]除以a+1/a-3
=[(a+2)(a-2)/(a-3)(a+2)+(a+2)/(a-3)] x(a-3)/(a+1)
=(a-2+a+2)/(a-3) x(a-3)(a+1)
=2a/(a+1)
如果本题有什么不明白可以追问,