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) 20/10/2021 Bởi Amara 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)
`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` Bình luận
#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` Bình luận
`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`
#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`