A=1+32+34+.....+32008
32A-A=1+32+34+....+32008+32010-[1+32+34+...+32008]
9A-A=32010
8A=32010
Mình làm vậy đúng hay sai.
A=1+32+33+34+......+32008
3A=3+33+34+35+......+32009
3A-A=(3+33+34+35.....+32009)-(1+32+33+34+...+32008)
A=(3+32009)-(1+32008)=(3+31+32008)-(1+32008)=3+3-1=5
Bạn làm sai rồi:))
Ta có\(A=1+3^2+3^4+...+3^{2008}\left(1\right)\)
\(\Rightarrow3^2A=3^2+3^4+3^6+...+3^{2010}\left(2\right)\)
Lấy (2) trừ (1) suy ra
\(3^2A-A=\left(3^2+3^4+3^6+...+3^{2010}\right)-\left(1+3^2+3^4+...+3^{2008}\right)\)
\(\Rightarrow8A=3^{2010}-1\Rightarrow A=\frac{3^{2010}-1}{8}\)
