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\(A=1+3+3^2+...+3^{2007}\)
\(\Rightarrow3A=3+3^2+3^3+...+3^{2008}\)
\(\Rightarrow3A-A=\left(3+3^2+3^3+...+3^{2008}\right)-\left(1+3+3^2+...+3^{2007}\right)\)
\(\Rightarrow2A=3+3^2+3^3+...+3^{2008}-1-3-3^2-...-3^{2007}\)
\(\Rightarrow2A=3^{2008}-1\)
\(\Rightarrow2A+1=3^{2008}\)
\(A=1+3+3^2+...+3^{2007}\)
\(\Rightarrow3A=3+3^2+3^3+...+3^{2008}\)
\(\Rightarrow3A-A=\left(3+3^2+3^3+...+3^{2008}\right)-\left(1+3+3^2+...+3^{2007}\right)\)
\(\Rightarrow2A=3+3^2+3^3+...+3^{2008}-1-3-3^2-...-3^{2007}\)
\(\Rightarrow2A=3^{2008}-1\)
\(\Rightarrow2A+1=3^{2008}\)
Nhớ k cho mk nha!!!
2A = 2 + 22 + 23 + ... + 2201
A = 2A - A = 2 + 22 + 23 + ... + 2201 - ( 1 + 2 + 22 + 23 + ... + 2200 )
= 2 + 22 + 23 + ... + 2201 - 1 - 2 - 22 - 23 - ... - 2200 = 2201 - 1
=> A + 1 = 2201 - 1 + 1 = 2201
Ta có: A=1+2+22+23+24+…+2200
=>2A=2+22+23+24+25+…+2201
=>2A-A=2+22+23+24+25+…+2201-1-2-22-23-24-…-2200
=>A=2201-1
=>A+1=2201
2A = 2 + 2^2+ 2^3+...+2^101
2A-A = 2^101- 1
=> A = 2^101- 1
=> A + 1 = 2^101
2A = 2 + 22 + 23 + ... + 2200 + 2201
2A - A = ( 2 + 22 + 23 +...+ 2200 + 2201 ) - ( 1 + 2 + 22 + 23 +...+ 2200 )
=> A = 2201 - 1
=> A +1= 2201
3A=\(3+3^2+3^3+...+3^{11}\)
3A-A=(\(3+3^2+3^3+...+3^{11}\))-(\(1+3+3^2+...+3^{10}\))
2A=\(3^{11}-1\)
2A+1=\(3^{11}\)
B = 1+6+6^2+6^3+...+6^8
6B=6^1+6^2+6^3+6^4+...+6^8+6^9
5B=6^9-1
=>5B+1=6^9
nhớ k cho mình nhé