Question

Xuannnn

想問這題～謝謝🙏

5
(3) 2012 (4) a2020
6. 等差數列中,若首項為正數且 S =S,下列敘述哪些正確?
(1)公差d>0
1993
人)7.設a 為一數列
U2000
(5) a2021
(2) a28 <0 (3) a28=0 (4) S35 = 0 (5)當n = 27 時 S, 有最大值
S=3n²+2n-2.下列選哪此正確?

故選(1)(4)
6.23 S32a24+ a25+...+a31 +932=000(001)
⇒a28X9=0⇒a28 = 0
(1) a₁>0 a28 = 0⇒d<0. +2XS
(2)(3) a28=0.+(1+X)X+(1
-
(49));
(4) S=55 (a₁ + ass) = 55 Xa28=0.
2
01 + (Q+... S+1)+(20+8+5+125
(5) n=27 28, S, Max.
200
故選(3)(4)(5).

Answer 1

xiaoqi

.