Ta có: A = 2 + 22 + 23 + ... + 22008
=> 2A = 22 + 23 + ... + 22009
=> 2A - A = 22009 - 2
=> A = 22009 - 2
Vậy A = 22009 - 2
=> 2A = 2.(22009 - 2)
=> 2A = 22010 - 4
=> 2A + 4 = 22010 - 4 + 4
=> 2A + 4 = 22010
=> 3x = 2010
Sai đề
\(A=2+2^2+2^3+...+2^{2008}\)
\(2A=2^2+2^3+2^4+...+2^{2009}\)
\(2A-A=\left(2^2+2^3+2^4+...+2^{2009}\right)-\left(2+2^2+2^3+...+2^{2008}\right)\)
\(A=2^{2009}-2\)
\(\Rightarrow2.\left(2^{2009}-2\right)+4=2^{3x}\)
\(\Rightarrow2^{2010}-4+4=2^{3x}\)
\(\Rightarrow2^{2010}=2^{3x}\)
=> 3x = 2010
=> x =670
\(A=2+2^2+2^3+...+2^{2008}\)
\(\Rightarrow2A=2^2+2^3+2^4+...+2^{2009}\)
\(\Rightarrow2A-A=2^{2009}-2\)
\(\Rightarrow A=2^{2009}-2\)
\(\Rightarrow2\left(2^{2009}-2\right)+4=2^{2010}-4+4=2^{2010}=2^{3x}\)
\(\Rightarrow2010=3x\Rightarrow x=670\)
vậy
mình sẽ k cho cả ba bạn nhà . thanks
