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26 tháng 6 2015

\(A=2+2^2+...+2^{20}\)

\(2A=2^2+2^3+...+2^{21}\)

\(\Rightarrow2A-A=\left(2^{21}+2^{20}+...+2^2\right)-\left(2^{20}+2^{19}+...+2^2+2\right)\)

\(\Rightarrow A=2^{21}-2\)

22 tháng 7 2023

\(2T=2^2+2^3+2^4+...+2^{2009}\)

\(T=2T-T=2^{2009}-2=2\left(2^{2008}-1\right)\)

22 tháng 7 2023

T= 2+22+23+...+22008

2T=22+23+24+...+22009

2T-T= 22009-2

T= 22009-2 = (22009-2)1

 

9 tháng 7 2016

\(0,001=\frac{1}{1000}=\frac{1}{10^3}=10^{-3}\)

\(0,0001=\frac{1}{10000}=\frac{1}{10^4}=10^{-4}\)

\(0,00015=\frac{3}{20000}=\frac{3}{2}\times\frac{1}{10000}=\frac{3}{2}\times\frac{1}{10^4}=\frac{3}{2}\times10^{-4}\)

\(5^{-a}=\frac{1}{5^a}\)

\(3,5\times10^{-5}=3,5\times\frac{1}{10^5}\)

\(\left(\frac{2}{3}\right)^{-2}==\frac{1}{\left(\frac{2}{3}\right)^2}=\left(\frac{3}{2}\right)^2\)

\(10^{-3}=\frac{1}{10^3}=\frac{1}{1000}\)

30 tháng 9 2018

a)\(\left(\frac{1}{5}\right)^{10}.5^{20}=\left(\frac{1}{5}\right)^{10}.5^{10.2}=\left(\frac{1}{5}\right)^{10}.25^{10}=\left(\frac{1}{5}.5\right)^{10}=1^{10}=1\)

b)\(5^2.3^5.\left(\frac{3}{5}\right)^2=\left(\frac{3}{5}.5\right)^2.3^5=3^2.3^5=3^7\)

c)\(\left(\frac{1}{16}\right)^3:\left(\frac{1}{8}\right)^2=\left(\frac{1}{8}\right)^{2.3}:\left(\frac{1}{8}\right)^2=\left(\frac{1}{8}\right)^{6+2}=\left(\frac{1}{8}\right)^8\)

30 tháng 9 2018

\(a.\left(\frac{1}{5}\right)^{10}.5^{20}=\left(\frac{1}{5}\right)^{10}.5^{10.2}=\left(\frac{1}{5}\right)^{10}.\left(5^2\right)^{10}=\left(\frac{1}{5}\right)^{10}.25^{10}=\left(\frac{1}{5}.25\right)^{10}=5^{10}.\)

\(b.5^2.3^5.\left(\frac{3}{5}\right)^2=\left[5^2.\left(\frac{3}{5}\right)^2\right].3^5=\left(5.\frac{3}{5}\right)^2.3^5=3^2.3^5=3^7\)\(c.\left(\frac{1}{16}\right)^3:\left(\frac{1}{8}\right)^2=\left[\left(\frac{1}{4}\right)^2\right]^3:\left[\left(\frac{1}{2}\right)^3\right]^2=\left(\frac{1}{4}\right)^6:\left(\frac{1}{2}\right)^6=\left(\frac{1}{4}:\frac{1}{2}\right)^6=\left(\frac{1}{2}\right)^6\)

a) 272 : 253

= (33)2 : (52)3

= 36 : 56

 \(=\left(\frac{3}{5}\right)^6\)

b) 254 : 28

= (52)4 : 28

= 58 : 28

\(=\left(\frac{5}{2}\right)^8\)

6 tháng 8 2023

(\(\dfrac{1}{9}\))2 = (\(\dfrac{1^2}{3^2}\))2= ((\(\dfrac{1}{3}\))2)2=  (\(\dfrac{1}{3}\))4

20 tháng 9 2023

\(\left(0,25\right)^8=\left[\left(0,5\right)^2\right]^8=\left(0,5\right)^{2.8}=\left(0,5\right)^{16}\)

\(\left(0,125\right)^4=\left[\left(0,5\right)^3\right]^4=\left(0,5\right)^{3.4}=\left(0,5\right)^{12}\)

\(\left(0,0635\right)^2=\left[\left(0,5\right)^3\right]^2=\left(0,5\right)^{3.2}=\left(0,5\right)^6\)

=>2A=2^3+2^4+...+2^2013

=>2A-A=A=(2^3+2^4+2^5+...+2^2013)-(2^2+2^3+2^4+...+2^2012)

=>A=2^2013-2^2