设级数$\sum\limits_{n=1}^\infty u_n$ 收敛，则下列级数收敛的是（） A: $\sum\limits_{n=1}^\infty \left(u_n+1\right)$ B: $\sum\limits_{n=1}^\infty u_{2n}$ C: $\sum\limits_{n=1}^\infty u_{n+1}$ D: $\sum\limits_{n=1}^\infty u_{2n+1}$

\( \mathop {\lim }\limits_{(x,y)______

运行“LIMITS”

下列级数中,收敛的是（ ）. A: \(<br/>\sum\limits_{n = 1}^\infty { { 1 \over n}} \) B: \(<br/>\sum\limits_{n = 1}^\infty { { 1 \over { { n^2}}}} \) C: \(<br/>\sum\limits_{n = 1}^\infty { { 1 \over {\sqrt n }}} \) D: \( \sum\limits_{n = 1}^\infty { { 1 \over {\root 3 \of { { n^2}} }}} \)

下列极限计算正确的是( ). A: \(\lim \limits_{x \to 0} { { \left| x \right|} \over x} = 1\) B: \(\lim \limits_{x \to {0^ + }} { { \left| x \right|} \over x} = 1\) C: \(\lim \limits_{x \to 0} {(1 - {1 \over {2x}})^{2x}} = {e^{ - 1}}\) D: \(\lim \limits_{x \to \infty } {(1 - {1 \over {2x}})^{2x}} = e\)

\( \lim \limits_{(x,y) \to (2,1)} (4x - 3y) =\)______ 。

\(\lim\limits_{(x,y)\to(3,2)}(4x - 3y) =\)______ 。

中国大学MOOC: Speed limits could rise with more people using self-driving cars. When self-driving cars prove they can 6) ______ at higher speed limits, speed limits could be raised.

AutoCAD设置绘图范围的命令是(),若选用metric(公制),默认的绘图范围是() A: LIMITS 12X9 B: LIMITS  420X297 C: LIMITS 297X210 D: ZOOM   420X297

\( \lim \limits_{x \to 0} { { \sin 3x} \over x} = \)______。______