Question

các ac giúp e với ạ 

e cảm ơn ac nhiều ạ 

Answer 1

\(A=\dfrac{1}{2}+\dfrac{1}{2^2}+\dfrac{1}{2^3}+...+\dfrac{1}{2^9}\)

\(\Rightarrow2A=1+\dfrac{1}{2}+\dfrac{1}{2^2}+...+\dfrac{1}{2^8}\)

\(\Rightarrow2A-A=1-\dfrac{1}{2^9}\)

\(\Rightarrow A=1-\dfrac{1}{2^9}=\dfrac{511}{512}\)

\(\Rightarrow\left(a+b\right)_{min}=511+512=1023\)