類題 5
小小叮寧-
可以硬解聯立求出a、d及n,
但是數字很醜
一個101項的等差數列a、az、03、
選項哪些正確?
(A) a, + a101 > 0
(D) asi = 51
diol,其和為0,且 as = 71,則下列
A
(B) az + 0101< 0
(E) a, < 0
(C) as + any = 0
85 推甄
o
數列細要具-
05
Su= artan
=
X X
2
8 +3
1 I
d d d d d di
5
as as as an ag ao aco.
類題。若數列〈an》為一等差數列且 a = 7,adio = 5,則下列哪些正確?68E
(A) a = 8
(B) Qoo
x= 29,4 (n.ind
3
(C)自第24 項開始為負
(D)前n項總和最大時,n=24 Myeo ,均為
(E)若前n项和 S. = pn= + qin + r,則p<0且r=0
7- ai + 3x ( - )
azo = 8 + 19 x (3) C24 = 8+ 23 × (-4)
2 8:59
=100
* E-
d a
zait(n-ud
Sna
d
24
u
3
)
d
d
q=0,- 2 r=0
z 424
25
4
23
18-a,
xhž xnt (arz)n 24 19
11
23