Question

1 .

a, tính tổng : B = 1+5+5 mũ hai+ 5 mũ ba+...+ 5 mũ 2008+ 5 mũ 2009

 

 

Answer 1

\(B=1+5+5^2+5^3+...+5^{2008}+5^{2009}\)

\(5B=5+5^2+5^3+5^4+...+5^{2009}+5^{2010}\)

\(4B=5^{2010}-1\)

\(B=\frac{5^{2010}-1}{4}\)

Answer 2

\(B=1+5+5^2+...+\)\(5^{2009}\)

\(\Rightarrow5B=5+5^2+5^3+...+5^{2010}\)

\(\Rightarrow5B-B=4B=5^{2010}-1\)

\(\Rightarrow B=\frac{5^{2010}-1}{4}\)

Answer 3

\(B=1+5+5^2+...+5^{2009}\)

\(5B=5+5^5+5^4+...+5^{2010}\)

\(5B-B=5^{2010}-1\)

\(4B=5^{2010}-1\)

\(B=\frac{5^{2010}-1}{4}\)

Answer 4

\(B=1+5+5^2+...+5^{2009}\)

\(=>5B=5+5^2+...+5^{2010}\)

\(=>5B-B=5^{2010}-1\)

\(=>B=\frac{5^{2010}-1}{4}\)