Đáp án:
a, `-19 + 2019^0 . (-3)^2`
=`-19 + 1 .9`
`=-19+9=-10`
c, ` 4/7 :( -2 3/5) + 4/7 . (-8/13) - 3/7`
`=4/7 : (-13/5) + 4/7 .(-8/13) - 3/7`
`=4/7 . (-5/13) + 4/7 .(-8/13) -3/7`
`=4/7 . ( -5/13 + (-8/13) ) -3/7`
`=4/7 . (-1) -3/7`
`=-4/7 - 3/7 =-7/7=-1`
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