\(1-2+3-4+5-6+...+2019-2020+2021\)

\(=\left(1+3+5+....+2021\right)-\left(2+4+6+...+2020\right)\)

\(=\left(\frac{\left(2021+1\right).1011}{2}\right)-\left(\frac{\left(2020+2\right).1010}{2}\right)\)

\(=\frac{2022.1011}{2}-\frac{2022.1010}{2}=\frac{2022}{2}=1011\)

...

Ra mỗi kết quả:

-1011

Sửa đề :

1 + 2 - 3 - 4 + 5 + 6 - 7 - 8 + 9 - ... + 2018 - 2019 - 2020 + 2021

= 1 + ( 2 - 3 - 4 + 5 ) + ( 6 - 7 - 8 + 9 ) + ... + ( 2018 - 2019 - 2020 + 2021 )

= 1 + 0 + 0 + ... + 0

= 1

hơ hơ.sao chép

S = 1 + 2 - 3 - 4 + 5 + 6 - 7 - 8 + ... + 2018 – 2019 - 2020 + 2021 + 2022

S = (1 + 2 - 3 - 4) + ... + (2017 + 2018 – 2019 - 2020) + 2021 + 2022

S = (-4) + ... + (-4) + 2021 + 2022

2020 : 4 = 505

S = (-4) . 505 + 2021 + 2022

S = (-2020) + 2021 + 2022

S = 2023

lỡ gửi nhầm bài

\(1-2+3-4+5-6+...+2019-2020+2021\)

\(=\left(1-2\right)+\left(3-4\right)+\left(5-6\right)+...+\left(2019-2020\right)+2021\)

\(=-1-1-1-..-1+2021\)

\(=-1\cdot1010+2021\)

\(=-1010+2021\)

\(=-1011\)

$1-2+3-4+5-6+...+2019-2020+2021$

$=\left(1-2\right)+\left(3-4\right)+\left(5-6\right)+...+\left(2019-2020\right)+2021$

$=-1-1-1-..-1+2021$

$=-1\cdot 1010+2021$

$=-1010+2021$

$=-1011$

=1+(2-3-4+5)+(6-7-8+9)+.....+(2018-2019-2020+2021)+2022

=1+0+0+.....+0+2022

=2023

số năm nay luôn

B=-1.1009+2019+2020+2021

Ta có: 1+2-3-4+5+6-7-8+.....-2019-2020+2021+2022

=1+(2-3-4+5)+(6-7-8+9)+.....+(2018-2019-2020+2021)+2022

=1+0+0+.....+0+2022

=2023

(1+3+5+7+...+2019+2021)

A=1−3+5−7+......−2019+2021−2023

A=(1−3)+(5−7)+....+(2021−2023)A=(1−3)+(5−7)+....+(2021−2023)

A=−2+(−2)+....+(−2)(506)A=−2+(−2)+....+(−2)(506cặp)

a=−2.506A=−2.506

A=−1012A=−1012

cảm ơn nhìu