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\(a,\Rightarrow2A=2+2^2+...+2^{2011}\)
\(\Rightarrow2A-A=2+2^2+...+2^{2011}-2^0-2-..-2^{2010}\)
\(\Rightarrow A=2^{2011}-1=B\)
\(b,A=2019.2011=\left(2010-1\right)\left(2010+1\right)=\left(2010-1\right).2010+\left(2010-1\right)=2010^2-2010+2010-1=2010^2-1< 2010^2=B\)
\(a,\Rightarrow2A=2^1+2^2+...+2^{2011}\\ \Rightarrow2A-A=A=2^{2011}-2^0=2^{2011}-1=B\)
\(b,A=\left(2010-1\right)\left(2010+1\right)=2010^2+2010-2010-1=2010^2-1< 2010^2=B\)
Bài 1:
\(a,A=\left(2+2^2\right)+\left(2^3+2^4\right)+...+\left(2^{2009}+2^{2010}\right)\\ A=\left(1+2\right)\left(2+2^3+...+2^{2009}\right)=3\left(2+...+2^{2009}\right)⋮3\\ A=\left(2+2^2+2^3\right)+...+\left(2^{2008}+2^{2009}+2^{2010}\right)\\ A=\left(1+2+2^2\right)\left(2+...+2^{2008}\right)=7\left(2+...+2^{2008}\right)⋮7\)
\(b,\left(\text{sửa lại đề}\right)B=\left(3+3^2\right)+\left(3^3+3^4\right)+...+\left(3^{2009}+3^{2010}\right)\\ B=\left(1+3\right)\left(3+3^3+...+3^{2009}\right)=4\left(3+3^3+...+3^{2009}\right)⋮4\\ B=\left(3+3^2+3^3\right)+...+\left(3^{2008}+3^{2009}+3^{2010}\right)\\ B=\left(1+3+3^2\right)\left(3+...+3^{2008}\right)=13\left(3+...+3^{2008}\right)⋮13\)
Bài 2:
\(a,\Rightarrow2A=2+2^2+...+2^{2012}\\ \Rightarrow2A-A=2+2^2+...+2^{2012}-1-2-2^2-...-2^{2011}\\ \Rightarrow A=2^{2012}-1>2^{2011}-1=B\\ b,A=\left(2020-1\right)\left(2020+1\right)=2020^2-2020+2020-1=2020^2-1< B\)
\(2A=2^1+2^2+...+2^{20}\)
\(\Leftrightarrow2A-A=2^1+2^2+...+2^{20}-2^0-...-2^{19}\)
\(\Leftrightarrow A=2^{20}-1\)
Vậy: A và B là hai số tự nhiên liên tiếp
Ta có :
\(A=2+2^2+2^3+2^4...2^{2010}\)\(^0\)
\(=2\left(1+2\right)+2^3\left(1+2\right)+...+2^{2009}\left(1+2\right)\)
\(=2.3+2^3.3+....+2^{2009}.3\)
\(=3\left(2+2^3+....+2^{2009}\right)⋮3\)
Ta có :
\(2+2^2+2^3+2^4+....+2^{2010}\)
\(=2\left(1+2+2^2\right)+2^4\left(1+2+2^2\right)+...+2^{2008}\left(1+2+2^2\right)\)
\(=2.7+2^4.7+....+2^{2008}.7\)
\(=7\left(2+2^4+....+2^{2008}\right)⋮7\)
Vậy \(2^1+2^2+2^3+2^4+...+2^{2010}⋮3\) và \(7\)
a) A = 2⁰ + 2¹ + 2² + 2³ + ... + 2²⁰²²
2A = 2 + 2² + 2³ + 2⁴ + ... + 2²⁰²³
A = 2A - A
= (2 + 2² + 2³ + 2⁴ + ... + 2²⁰²³) - (2⁰ + 2¹ + 2² + 2³ + ... + 2²⁰²²)
= 2²⁰²³ - 2⁰
= 2²⁰²³ - 1
Vậy A = B
b) A = 2021 . 2023
= (2022 - 1).(2022 + 1)
= 2022.(2022 + 1) - 2022 - 1
= 2022² + 2022 - 2022 - 1
= 2022² - 1 < 2022²
Vậy A < B
a) Ta có:
A = 1 + 21 + 22 + ... + 22010
=> 2A = 2 + 22 + 23 + ... + 22011
=> 2A - A = (2 + 22 + 23 + ... + 22011) - (1 + 2 + 22 + ... + 22010)
=> A = 22011 - 1
Mà B = 22011 - 1
=> A = B.
b) Ta có:
A = 2009 . 2011
=> A = 2009 . (2010 + 1)
=> A = 2009 . 2010 + 2009
Lại có:
B = 20102
=> B = 2010 . 2010
=> B = (2009 + 1) . 2010
=> B = 2009 . 2010 + 2010
Mà 2009 . 2010 + 2009 < 2009 . 2010 + 2010
=> A < B.
d)
Ta có:
A = 333444
=> A = 3334.111
=> A = (3334)111
Lại có:
B = 444333
=> B = 4443.111
=> B = (4443)111
Xét:
3334 = (3.111)4 = 34 . 1114 = 81 . 1114
4443 = (4.111)3 = 43 . 1113 = 64 . 1113
Ta thấy 81 . 1114 > 64 . 1113 => (3334)111 > (4443)111
=> A > B.
e)
Ta có:
A = 3450
=> A = 33.150
=> A = (33)150
B = 5300
=> B = 52.150
=> B (52)150
Mà (33)150 > (52)150
=> A > B.
Chúc bạn học tốt!
P/s: phần c hình như hơi sai đề mk nghĩ ko ra!