说明：此题不完整.
应该是“求极限lim(x->2)(x^2－6x＋8)/(x^2＋x－6)”.
原式=lim(x->2){[(x-2)(x-4)]/[(x-2)(x+3)]}
=lim(x->2)[(x-4)/(x+3)]
=(2-4)/(2+3)
=-2/5