`text{Cách 1:}`
`8/19 . (-15/17) + 4/17 . 2/19 + 4/19 . 28/17`
=`\frac{8 . (-15)}{19 . 17}` + `\frac{4 . 2}{19 .17}` + `\frac{4.28}{19.17}`
= `\frac{-120}{19.17}` + `\frac{8}{19.17}` + `\frac{112}{19.17}`
= `\frac{-120 + 8 + 112}{19.17}`
= `\frac{0}{19.7}`
`=0`
----------------------------------------------------
`text{Cách 2 :}`
`8/19 . (-15/17) + 4/17 . 2/19 + 4/19 . 28/17`
`=-120/323 + 4/19 . 2/17 + 4/19 . 28/17`
`= -120/323 + 4/19 . ( 2/17 + 28/17)`
`= -120/323 + 4/19 . 30/17`
`= -120/323 + 120/323`
`= 0/323`
`= 0`
