minh nghi ban dang chep sai de bai 

the de bai cua minh thi giai nhu sau

A=1/2015.2016+1/2016.2017+......+1/2029.2030

A=1/2015-1/2016+1/2016-1/2017+.....+1/2029-1/2030

A=1/2015-1/2030=3/818090

\(=\dfrac{97}{60};=\dfrac{5}{12}\)

\(\dfrac{97}{80}\)

\(\dfrac{5}{12}\)

Ta có A = 2⁰ + 2¹+2² + .. +2²⁰²⁹

       2A  = 2¹+2² + .. +2²⁰²⁹ + 2²⁰³⁰  

Lấy 2A - A :  2¹+2² + .. +2²⁰²⁹ + 2²⁰³⁰ - 2⁰ + 2¹+2² + .. +2²⁰²⁹

              A :2²⁰³⁰ - 1

Vậy A = 2²⁰³⁰ - 1

D

D

D

= (1-2015).(2-2015)....(2015-2015)....(2029-2015).(2030-2015)

= (1-2015).(2-2015)....0....(2029-2015).(2030-2015)

= 0

= (2021+2029) + (2022+2028) + (2023+2027) + (2024+2026) + 2025

= 4050 + 4050 + 4050 + 4050 + 2025

= 8100 + 4050 +4050 + 2025

= 12 150 + 4050 + 2025

= 16 200 +2025

= 18 225

nếu đúng tick dùm mik nhé

2021+2029+2022+2028+2023+2027+2024+2026+2025
Bằng bao nhiêu bạn tự tính ra nhé

2021+2022+2023+2024+2025+2026+2027+2028+2029

=(2021+2029)+(2022+2028)+(2023+2027)+(2024+2026)+2025

=4050+4050+4050+4050+2025

=4050.4+2025

=16200+2025

=18225

C=(1-5-9+13)+(17-21-25+29)+...+(2013-2017-2021+2025)-2029

C=0+0+0+...+0-2029

C=-2029

C = 1 - 5 - 9 + 13 + 17 - 21 - 25 + 29 + ... + 2013 - 2017 - 2021 + 2025 - 2029

= (1 - 5 - 9 + 13) + (17 - 21 - 25 + 29) + ... + (2001 - 2005 - 2009 + 2013) - 2017 - 2021 + 2025 - 2029

= 0 + 0 + ... + 0 - 4042

= -4042

cảm ơn

Đặt \(A=x^2-xy+y^2-3x-3y+2029\)

\(\Leftrightarrow2A=2x^2-2xy+2y^2-6x-6y+4058\)

\(\Leftrightarrow2A=\left(x^2-2xy+y^2\right)+\left(x^2-6x+9\right)+\left(y^2-6y+9\right)+4040\)

\(\Leftrightarrow2A=\left(x-y\right)^2+\left(x-3\right)^2+\left(y-3\right)^2+4040\ge4040\forall x;y\)

\(\Leftrightarrow A\ge\dfrac{4040}{2}=2020\forall x;y\)

Dấu " = " xảy ra \(\Leftrightarrow\left\{{}\begin{matrix}x-y=0\\x-3=0\\y-3=0\end{matrix}\right.\Leftrightarrow\left\{{}\begin{matrix}x=y\\x=3\\y=3\end{matrix}\right.\) \(\Leftrightarrow x=y=3\)

Vậy GTNN của b/t trên là : \(2020\Leftrightarrow x=y=3\)

1208 viết dưới dạng số la mã là : MCCVIII

2029 viết dưới dạng số la mã là : MMXXIX

1208:MCCVIII

2029 :MMXXIX