bryant_.log
로그인
bryant_.log
로그인
등차수열(arithmetic sequence), 등비수열(geometric sequence)
Bryant
·
2025년 10월 23일
팔로우
0
0
수학
목록 보기
8/8
등차수열
a
n
=
a
1
+
(
n
−
1
)
d
S
n
=
a
1
+
a
2
+
.
.
.
+
(
a
1
+
(
n
−
1
)
d
)
a_n = a_1 +(n-1)d \\S_n= a_1+a_2+...+(a_1+(n-1)d)
a
n
=
a
1
+
(
n
−
1
)
d
S
n
=
a
1
+
a
2
+
.
.
.
+
(
a
1
+
(
n
−
1
)
d
)
역순끼리 더하면
S
n
=
a
1
+
(
a
2
+
d
)
+
.
.
.
+
(
a
1
+
(
n
−
1
)
d
)
S
n
=
(
a
1
+
(
n
−
1
)
d
)
+
(
a
1
+
(
n
−
2
)
d
)
+
.
.
.
+
a
1
2
S
n
=
(
2
a
1
+
(
n
−
1
)
d
)
+
(
2
a
1
+
(
n
−
1
)
d
)
+
.
.
.
2
S
n
=
n
(
2
a
1
+
(
n
−
1
)
d
S
n
=
n
2
(
2
a
1
+
(
n
−
1
)
d
)
S_n= a_1+(a_2+d)+...+(a_1+(n-1)d) \\S_n= (a_1+(n-1)d)+(a_1+(n-2)d) +... +a_1 \\2S_n = (2a_1+(n-1)d)+(2a_1+(n-1)d)+... \\2S_n = n(2a_1+(n-1)d \\S_n = \frac{n}{2}(2a_1+(n-1)d)
S
n
=
a
1
+
(
a
2
+
d
)
+
.
.
.
+
(
a
1
+
(
n
−
1
)
d
)
S
n
=
(
a
1
+
(
n
−
1
)
d
)
+
(
a
1
+
(
n
−
2
)
d
)
+
.
.
.
+
a
1
2
S
n
=
(
2
a
1
+
(
n
−
1
)
d
)
+
(
2
a
1
+
(
n
−
1
)
d
)
+
.
.
.
2
S
n
=
n
(
2
a
1
+
(
n
−
1
)
d
S
n
=
2
n
(
2
a
1
+
(
n
−
1
)
d
)
a
n
=
a
1
+
(
n
−
1
)
d
이므로
,
S
n
=
n
2
(
a
1
+
a
n
)
도 표현가능
a_n = a_1+(n-1)d~이므로, \\S_n = \frac{n}{2}(a_1+a_n)도 ~표현 가능
a
n
=
a
1
+
(
n
−
1
)
d
이
므
로
,
S
n
=
2
n
(
a
1
+
a
n
)
도
표
현
가
능
등비수열
a
n
=
a
1
r
n
−
1
S
n
=
a
1
+
a
1
r
+
a
1
r
2
+
.
.
.
+
a
1
r
n
−
1
r
S
n
=
a
1
r
+
a
1
r
2
+
a
1
r
3
+
.
.
.
+
a
1
r
n
(
1
−
r
)
S
n
=
a
1
−
a
1
r
n
=
a
1
(
1
−
r
n
)
S
n
=
a
1
1
−
r
n
1
−
r
a_n = a_1r^{n-1} \\S_n = a_1+a_1r+a_1r^2+...+a_1r^{n-1} \\rS_n = a_1r+a_1r^2+a_1r^3+...+a_1r^{n} \\(1-r)S_n = a_1-a_1r^n =a_1(1-r^n) \\S_n = a_1\frac{1-r^n}{1-r}
a
n
=
a
1
r
n
−
1
S
n
=
a
1
+
a
1
r
+
a
1
r
2
+
.
.
.
+
a
1
r
n
−
1
r
S
n
=
a
1
r
+
a
1
r
2
+
a
1
r
3
+
.
.
.
+
a
1
r
n
(
1
−
r
)
S
n
=
a
1
−
a
1
r
n
=
a
1
(
1
−
r
n
)
S
n
=
a
1
1
−
r
1
−
r
n
Bryant
Data analysis, statistics
팔로우
이전 포스트
벡터의 내적 (inner product)
0개의 댓글
댓글 작성
