Question

☁️

（C）看不懂🙏🏻

範例4
指、對數形成的數列與級數
綜合 10.
已知a1,a2,ds,...,a是首項為-3,公差為一的等差數列,設b=2x2-3x23x2aux... x 2(-1)atlan
,試選出正確的選項。 (B)(D)(E)
(A) log2 (b12) = 2
(B) log2 (b21)
= 13
(D)log: (bz),logz (ba),log(b),log(b),...為等差數列
(E)log: (b),log2(b),log2(b),log(b),...為等差數列
an=q+(n-1)d=-3+ 2 (n-1)=
n-10
3
,
bn=29-a2+a3-94+...+(-1)+la
=...=91-92=-d=-1
(A)b2=21-a2+a3-9q+..+G1-G2, 又aq-d2=93-dq="
(B) b21 = 21-a2+a3-a4+ ··· +a19-20 × 2921 = (2
log2(62) = log2.
1
4
=-
1×23 = 23, log2(621)
3
(C) bn+1 = 2-3 xb
(C).
④提示
bn+2
=
:2(-1)h+2an.
<2(-1)+3d
an+2
bn
·an+1.
x
(D(E)利用(C)的結果,檢查
log₂ (bn+2)-log(bn)
(bn+2)
= log2(-
bn
1 1 1
1 1
所以b12 =
= 2 3
3 3
3
3
字= 2-2 =
1
=
⇒
4
21-10
10
=2言,
解
bn+2
=
(C)(D)(E) =2(-1)+2an+1x2(-1)2+3 a
Dan+2=2(-1)n+2(an+1-an+2) =2
(-1)+(-)
bm
bn
若n 為偶數,則 Da+2 = 25 ⇒ log:(benz)-log:(b)=log:(02)=log:(23)=-13
bn
若n為奇數,則
bn+2= 23
bn
→ log:(bntz)-logz(b)=log:(012)=
bnx2)=log:(23) = 2
bn
3
故(D)是公差為 - 1 的等差數列,(E)是公差為 ㄒㄧㄣ 的等差數列

Answer 1

丁輝人的貓

兩項相除就知道不是對的了