Tính bằng cách thuận tiện: a) -7264 + (1543 + 7264) + (144 – 97) –144 b) (-145) – (18 – 145) – [111 + (-11 + 27)] c) (27 + 514) – (486 – 73) + (36 + 79) + (145 – 79 – 36) d) d) -23 . 63 + 23 . 21 – 58 . 23

`a)`

`-7264 + ( 1543 + 7264 ) + ( 144 - 97 ) - 144`

`= -7264 + 1543 + 7264 + 144 - 97 - 144`

`= ( -7264 + 7264 ) + ( 144 - 144 ) + ( 1543 - 97 )`

`= 0 + 0 + 1446`

`= 1446`

`b)`

`( -145 ) - ( 18 - 145 ) - [ 111 + ( -11 + 27 ) ]`

`= -145 - 18 + 145 - [ 111 - 11 + 27 ]`

`= ( -145 + 145 ) - 18 - 111 + 11 - 27`

`= 0 - 18 + ( -111 + 11 ) - 27`

`= ( -18 - 27 ) + ( -100 )`

`= -45 - 100`

`= -145`

`c)`

`( 27 + 514 ) - ( 486 - 73 ) + ( 36 + 79 ) + ( 145 - 79 - 36 )`

`= 27 + 514 - 486 + 73 + 36 + 79 + 145 - 79 - 36`

`= ( 27 + 73 ) + ( 514 + 486 ) + ( 36 - 36 ) + ( 79 - 79 ) + 145`

`= 100 + 1000 + 0 + 0 + 145`

`= 1100 + 145`

`= 1245`

`d) `

`-23. 63 + 23. 21 - 58. 23`

`= 23. ( -63 ) + 23. 21 - 58. 23`

`= 23. ( -63 + 21 - 58 )`

`= 23. ( -100 )`

`= -2300`