1, -25.72+25.21-49.25 2, 35(14-23)-23(14-35) 3, 8154-(674+8154)+(-98+674) 4, -25.21+25.72+49.25 5, 27(13-16)-16(13-27) Đề bài: tính hợp lí nhất

0 bình luận về “1, -25.72+25.21-49.25 2, 35(14-23)-23(14-35) 3, 8154-(674+8154)+(-98+674) 4, -25.21+25.72+49.25 5, 27(13-16)-16(13-27) Đề bài: tính hợp lí nhất”

1. $#Dino$

   `a) -25.72+25.21-49.25`

   `=25(-72+21-49)`

   `=25.(-100)`

   `=-2500`

   ………………..

   `b) 35.(14-23)-23.(14-35)`

   `=35.14-35.23-23.14+23.35`

   `=35.(-23+23)+14(35-23)`

   `=0+14.12`

   `=168`

   ……………………

   `c) 8154-(674+8154)+(-98+674)`

   `=8154-8154-674+674-98`

   `=-98`

   ………………………….

   `d) -25.21+25.72+49.25`

   `=25(-21+72+49)`

   `=25.100`

   `=2500`

   …………………

   `e) 27.(13-16)-16(13-27)`

   `=27.13-27.16-16.13+16.27`

   `=13.(27-16)+16(-27+27)`

   `=13.11+0`

   `=143`

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2. `1, – 25 . 72 + 25 . 21 – 49 , 25`

   `= 25 . ( – 72 ) + 25 . 21 – 49 . 25`

   `= 25 . [ ( – 72 ) + 21 – 49 ) ]`

   `= 25 .  ( – 100 )`

   `= – 2500`

   `2, 35 . ( 14 – 23 ) – 23 . ( 14 – 35 )`

   `= 35 . 14 – 35 . 23 – 23 . 14 + 23 . 25`

   `= 35 .  ( 23 – 23 ) + 14 . ( 35 – 23 )`

   `= 35 . 0 + 14 . 12`

   `= 0 + 168`

   `= 168`

   `3, 8154 – ( 674 + 8154 ) + ( – 98 + 674 )`

   `= 8154 – 674 – 8154 + ( – 98 ) + 674`

   `= ( 8154 – 8154 ) + ( – 98 ) – ( – 674 + 674 )`

   `= 0 + ( – 98 ) – 0`

   `= ( – 98 )`

   `4, – 25 . 21 + 25 . 72 + 49 . 25`

   `= 25 . ( – 21 ) + 25 . 72 + 49 . 25`

   `= 25 . [ ( – 21 ) + 72 + 49 )`

   `= 25 . 100`

   `= 2500`

   `5, 27 . ( 13 – 16 ) – 16 . ( 13 – 27 )`

   `= 27 . 13 – 27 . 16 – 16 . 13 + 16 . 27`

   `= 13 . ( 27 – 27 ) + 13 . ( 27 – 16 )`

   `= 13 . 0 + 13 . 11`

   `= 0 + 143`

   `= 143`

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