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\(B=4+2^2+2^3+...+2^{20}\)
\(2B=8+2^3+2^4+...+2^{21}\)
\(2B-B=\left(8+2^3+2^4+...+2^{21}\right)-\left(4+2^2+2^3+...+2^{20}\right)\)
\(B=8+2^{21}-\left(4+2^2\right)=2^{21}\)
\(\Rightarrow2A=8+2^3+...+2^{2022}\\ \Rightarrow2A-A=8+2^3+...+2^{2022}-4-2^2-...-2^{2021}\\ \Rightarrow A=8+2^{2022}-4-2^2=8-4-4+2^{2022}=2^{2022}\left(đpcm\right)\)
\(A=2^2+2^2+2^3+...+2^{2021}=2^3+2^4+...+2^{2021}=2^{2022}\left(đpcm\right)\)
A=1+2+22+...+230
2A=2+22+23+...+231
2A-A=(2+22+23+...+231)-(1+2+22+...+230)
A=231-1
=>A+1=231-1+1=231
a=1+2+2^2+.......+2^30
2a=2(1+2+2^2+...+2^30)
2a=2+2^2+2^3+...2^31
2a-a=(2+2^2+2^3+...+2^31)-(1+2+2^2+2^30)
triệt tiêu ta có
a=2^31-1
a+1=2^31-1+1
a+1=2^31
\(\Rightarrow2B=8+2^3+2^4+...+2^{21}\\ \Rightarrow2B-B=2^{21}+8-4-2^2=2^{21}\)
3.
a) 4.4.4.4.4 = 45
b) 3.3.3.5.5.5 = 33 . 53
4.
a) 35 . 34 = 39
b) 53 . 55 = 58
c) 22
Hk tốt
\(12^2.3.12^3.4=\left(4.3\right)^2.3.4=4^2.3^2.3.4=3^3.4^3=27.64=1728\)
\(12^2.3.12^3.4=12^5.3.4=\left(3.4\right)^5.3.4=3^5.4^5.3.4=3^6.4^6=729.4096=\text{2985984}\)
ko biết