(12346^2-12345*13247)/24690 =[12346^2-(12346-1)*(12346+1)]/24690 =(12346^2-12346^2+1)/24690 =1/24690
12346^2-12345*12347分之24690=?
(12346^2-12345*13247)/24690 =[12346^2-(12346-1)*(12346+1)]/24690 =(12346^2-12346^2+1)/24690 =1/24690