thực hiện phép tính nhanh nếu có thể:a,5.(-8).2.(-3);b,3.(-5)^2+2.(-5)-20,c,34.(15-10)-15.(34-10)

Question

thanhbinh · Answer

`a,5.(-8).2.(-3)`

`=[5.(-8)].[2.(-3)]`

`=-40.(-6)`

`=240`

`b,3.(-5)^2+2.(-5)-20`

`=3.25+2.(-5)-20`

`=5.(3.5-2-4)`

`=5.9`

`=45`

`c,34.(15-10)-15.(34-10)`

`=34.15-34.10-15.34+15.10`

`=(34.15-15.34)-(34.10-15.10)`

`=0-(34-15).10`

`=-190`

tuvi · Answer

#KhanhHuyen2006

`a) 5 . (-8) . 2 . (-3)`

`= (5 . 2) . [(-8) . (-3)]`

`= 10 . 24`

`= 240`

`b) 3 . (-5)^2 + 2 . (-5) – 20`

`= 3 . 25 + 2 . (-5) – 20`

`= 5 (3 . 5 – 2 – 4)`

`= 5 . 9`

`= 45`

`c) 34 . (15 – 10) – 15 . (34 – 10)`

`= 34 . 15 – 34 . 10 – 15 . 34 – 15 . 10`

`= 15 . (34 – 34 – 10) – 34 . 10`

`= 15 . (-10) – 34 . 10`

`= -15 . 10 – 34 . 10`

`= 10 . [-15 – 34]`

`= 10 . (-19)`

`= -190`