ans

012508
$(-2,0]$

012509
$4$

012510
$36\pi$

012511
$35$

012512
$2$

012513
$3$

012514
$y=3x-1$

012515
$\dfrac 25$

012516
$-1$

012517
$\cos(4x+\dfrac \pi 3)$

012518
$\dfrac{49}{24}\sqrt{6}$

012519
\textcircled{1}\textcircled{4}

012520
A

012521
D

012522
B

012523
C

012524
(1) $\dfrac \pi 3$; (2) 证明略

012525
(1) $a_n=2n$; (2) $6$

012526
(1) 证明略; (2) $\dfrac{2\sqrt{42}}7$; (3) 存在, $|A_1E|=1$

012527
(1) $X\sim \begin{pmatrix}  155 & 165 & 175 & 185 & 195 & 205\\ 0.22 & 0.27 & 0.25 & 0.15 & 0.1 & 0.01\end{pmatrix}$, $E[X]=171.7$; (2) $0.0312$; (3) $27.25$

012528
(1) 在$(-\infty,2-\dfrac{\sqrt{3a}}3]$上是严格增函数, 在$[2-\dfrac{\sqrt{3a}}3,2+\dfrac{\sqrt{3a}}3]$上是严格减函数, 在$[2+\dfrac{\sqrt{3a}}3,+\infty)$上是严格增函数; (2) 是定值$6$; (3) $\{4,12\}$

12676
$(-2,1)$

12677
$4$

12678
$(-\infty,2)$

12679
$80$

12680
$\dfrac\pi 2$

12681
$-7$

12682
$0.36$

12683
$12$

12684
$\dfrac{18}{35}$

12685
$8$

12686
$(-\pi,-\dfrac\pi 2)$和$(0,\dfrac\pi 2)$

12687
$9$

12688
B

12689
D

12690
B

12691
D

12692
(1) $a_n=5-n$; (2) $n=4$或$5$

12693
(1) 证明略; (2) $\dfrac 14$

12694
(1) $247.4$米; (2) $AB=AD=100\sqrt{5}$米, $\angle C=\dfrac\pi 2$

12695
(1) $F_1(-\sqrt{3},0)$, $F_2(\sqrt{3},0)$, $e_1=\dfrac{\sqrt{3}}2$; (2) $2$; (3) 证明略

12696
(1) $f_1(x)$不是$T(1)$函数, $f_2(x)$是$T(1)$函数; (2) 存在, $b$的取值范围为$(1-\dfrac 1{\mathrm{e}},+\infty)$; (3) 证明略