\(\frac{99}{98}-\frac{98}{97}+\frac{1}{97\times98}\)
\(=\left(1+\frac{1}{98}\right)-\left(1+\frac{1}{97}\right)+\frac{1}{97\times98}\)
\(=\frac{1}{98}-\frac{1}{97}+\frac{1}{97\times98}\)
\(=\frac{-1}{97\times98}+\frac{1}{97\times98}\)
\(=0\)
\(\frac{99}{98}-\frac{98}{97}+\frac{1}{97X98}=\left(1+\frac{1}{98}\right)-\left(1+\frac{1}{97}\right)+\frac{1}{97X98}\)
\(=\frac{1}{97X98}-\frac{1}{97X98}=0\)
Nguyễn tuấn thảo ơi người ta mới lớp 5 bạn thêm -1 vào chi ? :)