lim（x^2-1）/(x^2-5x+4) x→1

x→2
lim (x^3-64) / (x^2-5x+4)
=lim (x-4)(x^2+4x+16) / (x-1)(x-4)
=lim (x^2+4x+16) / (x-1)
=(2^2+4*2+16) / (2-1)
=28
有不懂欢迎追问