60%f（x）[a+）|f（x）|N|f（x）|f（a）=0.N0:f（x）=040%ABnnnPQAP=BBQ=A（1）nnKP+（PQEn）K（2）nnCAC=B.ABRnnrank（ABA）=rankB.ABBA.yueLightning##+