`1.`
`(-0,5)^3.(-0,5)`
`=(-0,5)^(3+1)`
`=(-0,5)^4`
`2.`
`a)`
`15/34+7/21+19/34-20/15+3/7`
`=15/34+7/21+19/34-4/3+3/7`
`=(15/34+19/34)+({-4}/3+3/7)+7/21`
`=1+{-19}/21+7/21`
`=3/7`
`b)`
`16{2}/7:(-3/5)-28{2}/7:(-3/5)`
`=16{2}/7.(-5/3)-28{2}/7.(-5/3)`
`=(-5/3).(16{2}/7-28{2}/7.)`
`=(-5/3).(-12)`
`=20`
`c)`
`2{1}/2+4/7:({-8}/9)`
`=5/2+4/7:({-8}/9)`
`=5/2+({-9}/14)`
`=13/7`
`d)`
`6-3.({-1}/3)^3`
`=6-3.(-1/27)`
`=6-({-1}/9)`
`=55/9`
`3.` Tìm $x$
`3/4+2/5x=29/60`
`<=>2/5x=29/60-3/4`
`<=>2/5x={-4}/15`
`<=>x={-4}/15:2/5`
`<=>x={-2}/3`
Vậy `x={-2}/3`
