Bán kính hội tụ của chuỗi \[\sum\limits_{n = 1}^\infty {\frac{{{x^n}}}{{{2^n} + {4^n}}}} \]

A. \[W = \left\{ {({x_1},{x_2},{x_3}/{x_1} = 0} \right\} \subset {R^3}\]

B. \[W = \left\{ {({x_1},{x_2},{x_3}/{x_1} = 1} \right\} \subset {R^3}\]

C. \[W = \left\{ {({x_1},{x_2},{x_3}/{x_1} + {x_2} = 1} \right\} \subset {R^3}\]

D. \[W = \left\{ {({x_1},{x_2},{x_3}/{x_2} = 3} \right\} \subset {R^3}\]

A. ∀m∈R

B. Không tồn tại m

C. \[m \ne 0 \wedge m \ne 1 \wedge m \ne - 1\]

D. \[m \ne 0 \vee m \ne 1 \vee m \ne - 1\]

A. \[\left\{ {{u_1} = \left( { - 2,1, - 1} \right),{u_1} = \left( {1, - 1, - 1} \right),{u_3} = \left( { - 1,0, - 2} \right)} \right\}\]

B. \[\left\{ {{u_1} = \left( {1,1,2} \right),{u_1} = \left( {1, - 1, - 1} \right),{u_3} = \left( {2,1,1} \right)} \right\}\]

C. \[\left\{ {{u_1} = \left( {1,1} \right);{u_2} = \left( { - 1,1} \right)} \right\}\]

A. r = 4

B. r = 1

C. r = \[\frac{1}{3}\]

D. r = \[\frac{1}{4}\]

A. 1

B. 2

C. 3

D. 4

A. m = 0

B. m = -1

C. m = 2

D. Đáp án khác

A. \[\left\{ {\left( {1,1,0} \right),\left( { - 1,0,1} \right)} \right\}\]

B. \[\left\{ {\left( {1,1,0} \right),\left( {0,0,1} \right)} \right\}\]

C. \[\left\{ {\left( {1,1,0} \right),\left( {0,1,0} \right)} \right\}\]

D. \[\left\{ {\left( {1,0, - 1} \right),\left( {0,1, - 1} \right)} \right\}\]