ans

17423
$-\dfrac 45$

17424
$(\dfrac 12,1)$

17425
$160$

17426
$9$

17427
$0$

17428
$\dfrac{\sqrt{6\pi}}{6}$

17429
$5$

17430
$\dfrac{2\sqrt{3}}{3}$

17431
$\dfrac{2}{3}$

17432
$4\sqrt{2}-3$

17433
$3+\dfrac{5\sqrt{3}}{3}$

17434
$(-1,0)$

17435
A

17436
C

17437
B

17438
A

17439
(1) $\dfrac 12$; (2) $(\dfrac{\sqrt{3}}{2},1]$


17440
(1) $4\sqrt{3}$; (2) 证明略

17441
(1) $\dfrac 57$; (2) $E[X]=1$, $D[X]=0.8$

17442
(1) $x^2-\dfrac{y^2}{3}=1$; (2) $1+\sqrt{2}$; (3) $(\sqrt{2},+\infty)$

17443
(1) $m=9$; (2) $\dfrac{4\sqrt{3}}{9}$; (3) 不存在, 证明略