2-4+6-8+...-2016+2018
=(2-4)+(6-8)+...+(2014-2016)+2018
có 504 cặp
=-2+-2+...+-2+2018
=-2x504+2018
=-1008+2018
=1010
2-4+6-8+...-2016+2018
= (2+6+...+2018)- (4+8+....+2016)
=510050 - 509040
= 1010
2-4+6-8+...-2016+2018
=(2-4)+(6-8)+...+(2014-2016)+2018
có 504 cặp
=-2+-2+...+-2+2018
=-2x504+2018
=-1008+2018
=1010
2-4+6-8+...-2016+2018
= (2+6+...+2018)- (4+8+....+2016)
=510050 - 509040
= 1010
2 + (- 4) + 6 + (-8) + 10 + ( -12) +......+2014 + ( - 2016) + 2018
B =2-4-6+8+10-12-14+.... -2014+2016+2018-2020
Tính nhanh
a) S1= 1+(-2)+3+(-4)+.......+2016+(-2017)
b) S2 = 2-4+6-8+..........+2016-2018
Bài 1:
a, C = 1 + 5^2 + 5^4 + 5^6 +...+ 5^2018
b, D = 2 x 4 + 4 x 6 + 6 x 8 + 8 x 10 + ... + 2016 x 2018
tính : 1 + 2 - 3 -4 + 5 + 6 - 7 - 8 + ... + 2013 + 2014 - 2015 - 2016 + 2017 + 2018
Tình hợp lí nếu có thể:2-4+6-8+...-2016+2018
Tính S = 1 - 2 - 3 + 4 + 5 - 6 - 7 + 8 +...+ 2016 + 2017 - 2018 - 2019 + 2020
2+3-4+5+6-7+8+9-10+...+2015+2016-2017+2018+2019-2020+2021+2022
Tính A= 2020-2018+2016-2014+...+8-6+4-2