答案是：(2*X)/((X - Z)*(X + Z))解题过程给我写下1=（2X+Z-Y)/[(x-y)(x+z)]-(y-z)/[(x-z)(x-y)] =[(2x+z-y)(x-z)-(y-z)(x+z)]/[(x-y)(x+z)(x-z)] =[2x(x-y)]/[(x-y)(x+z)(x-z)] =(2*X)/((X - Z)*(X + Z))