a是负数,a和1/a比较大小(提示:分3种情况看,-1<a<0,a=-1,a<-1)
当-1< a < 0 时, 可假设a = -1/2,
则1/a = -2 ,故 a > 1/a
当 a= -1 时, 1/a = -1 ; 故a = 1/a
当a < -1 时, 可假设a = -2 ,
则 1/a = -1/2 , 故 a < 1/a
当-1< a < 0 时, 可假设a = -1/2,
则1/a = -2 ,故 a > 1/a
当 a= -1 时, 1/a = -1 ; 故a = 1/a
当a < -1 时, 可假设a = -2 ,
则 1/a = -1/2 , 故 a < 1/a