a. 5.(–8).( –2).(–3) b) 53 – (–51) + (-53) + 49 c) 100 + (+430) + 2145 + (-530) d) – 75. (18 – 65) – 65. ( 75 – 18) e) A = 2 + (-3) + 4 + (-5) + … + 2008 + (-2009) + 2010 + (-2011) + 2012.
a. 5.(–8).( –2).(–3) b) 53 – (–51) + (-53) + 49 c) 100 + (+430) + 2145 + (-530) d) – 75. (18 – 65) – 65. ( 75 – 18) e) A = 2 + (-3) + 4 + (-5) + … + 2008 + (-2009) + 2010 + (-2011) + 2012.
Đáp án:
Giải thích các bước giải:
a. 5.(–8).( –2).(–3)
=- 40 . 6
= -240
b) 53 – (–51) + (-53) + 49
= 53 + 51 + (-53) +49
= 53+ (-53) + 51 +49
= 0 + 100
= 100
c) 100 + (+430) + 2145 + (-530)
=100 + 2145 + 430 + (-530)
= 2245 + (-100)
= 2145
d) – 75. (18 – 65) – 65. ( 75 – 18)
= – 75. 18 – ( -75) . 65 – 65. 75 + 65 . 18
= – 75. 18 + 75 . 65 – 65. 75 + 65 . 18
= 18 . ( – 75 + 65 )
= 18 . (-10)
= -180
e) A = 2 + (-3) + 4 + (-5) + … + 2008 + (-2009) + 2010 + (-2011) + 2012.
A = -1 + ( -1) + (-1) + ….. + (-1) ( có 1006 số ( -1)
A = – 1006
a, 5 . ( -8 ) . ( -2 ) . ( -3 )
= 5 . 8 . 2 . ( -3 )
= ( 5 . 8 ) . ( -3 . 2 )
= 40 . ( -6 )
= -240
b, 53 – ( -51 ) + ( -53 ) + 49
= 53 + 51 – 53 + 49
= ( 53 – 53 ) + ( 51 + 49 )
= 0 + 100
= 100
c, 100 + ( +430 ) + 2145 + ( -530 )
= 100 + 430 + 2145 – 530
= ( 2145 + 100 ) – ( 540 – 430 )
= 2245 – 100
= 2145
d, – 75 . ( 18 – 65 ) – 65 . ( 75 – 18 )
= ( -75 ) . 18 + 75 . 65 – 65 . 75 + 65 . 18
= 65 . 18 – 75 . 18
= 18 . ( -10 )
= -180
e, A = 2 + ( -3 ) + 4 + ( -5 ) + … + 2008 + ( -2009 ) + 2010 + ( -2011 ) + 2012
A = 2 – 3 + 4 – 5 + … + 2008 – 2009 + 2010 – 2011 + 2012
A = ( 2 – 3 ) + ( 4 – 5 ) + … + ( 2010 – 2011 ) + 2012 ( có 1005 cặp số )
A = ( -1 ) + ( -1 ) + … + ( -1 ) + 2012 ( có 1005 số hạng -1 )
A = 1005 . ( -1 ) + 2012
A = 2012 – 1005
A = 1007
Vậy A = 1007