Question

Answer 1

Công bội: \(q=\dfrac{u_2}{u_1}=\dfrac{1}{3}\)

Đáp án C

Answer 2

Ta có: \(u_n=u_1\cdot q^{n-1}\) với \(n\ge2\)

\(\Rightarrow u_2=u_1\cdot q^{2-1}\Rightarrow1=3\cdot q\)

\(\Rightarrow q=\dfrac{1}{3}\)

Chọn C

Answer 3

c

Answer 4

\(ADCT:u_n=u_1.q^{n-1}\left(n\ge2\right)\\ \Rightarrow u_2=u_1.q\\ \Leftrightarrow1=3.q\\ \Leftrightarrow q=\dfrac{1}{3}\\ \Rightarrow C\)