Barisan Geometri
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Transcript Barisan Geometri
Barisan dan Deret
Geometri
By: Jeffrey Bivin
Lake Zurich High School
[email protected]
Last Updated: October 11, 2005
Barisan Geometri
1, 2, 4, 8, 16, 32, … 2n-1, …
3, 9, 27, 81, 243, … 3n, . . .
81, 54, 36, 24, 16,
n 1
2
… 81 , . .
3
34 2 n 1
2 n 1
n 5
n 1
3
3
Jeff Bivin -- LZHS
.
Barisan Geometri Suku Ke-n
Un =
Jeff Bivin -- LZHS
(n-1)
a·r
Menentukan Rumus Barisan
Geometri
Suku Pertama 2
Rasio 3
Jeff Bivin -- LZHS
un =
(n-1)
a·r
un =
(n-1)
2(3)
Tentukan rumus barisan
geometri Un
Un =
Suku Pertama 128
Rasio (1/2)
(n-1)
a·r
1
U n 128
2
n 1
1
U n 2 n 1
2
7
Jeff Bivin -- LZHS
Un
1
2
n 8
Tentukan rumus barisan
geometri suku ke- n atau Un
Un =
Suku pertama 64
Rasio (3/2)
(n-1)
a·r
3
U n 64
2
n 1
3
U n 2 n 1
2
n 1
6
Jeff Bivin -- LZHS
n 1
3
U n n 7
2
Menentukan Nilai Suku Ke-10
a=3
r=2
n = 10
Jeff Bivin -- LZHS
3, 6, 12, 24, 48, . . .
(n-1)
a·r
Un =
10-1
U10 = 3·(2)
9
U10 = 3·(2)
U10 = 3·(512)
U10 = 1536
Menentukan Suku Ke-8
a= 2
r = -5
n=8
Jeff Bivin -- LZHS
2, -10, 50, -250, 1250, . . .
(n-1)
a·r
Un =
8-1
Un = 2·(-5)
7
Un = 2·(-5)
Un = 2·(-78125)
Un = -156250
Menjumlahkan Deret Geometri
Sn
Jeff Bivin -- LZHS
n
a
i 1
r
n 1
a a.r
1 r
n
1 + 3 + 9 + 27 + 81 + 243
a ar
Sn
1 r
6
1 1 3
Sn
1 3
1 729
Sn
2
728
Sn
364
2
n
a=1
r=3
n=6
Jeff Bivin -- LZHS
4 - 8 + 16 - 32 + 64 – 128 + 256
a ar
Sn
1 r
7
4 4 (2)
Sn
1 (2)
4 4(128)
Sn
3
4 512 516
Sn
172
3
3
n
a=4
r = -2
n=7
Jeff Bivin -- LZHS
Alternative Sum Formula
Kita tahu bahwa:
a ar
Sn
1 r
n 1
U n ar
n
n 1
U n r ar r
n
Sederhanakan:
U n r ar
Dikalikan r:
Substitusikan:
Jeff Bivin -- LZHS
a Un r
Sn
1 r
Tentukan jumlah barisan
geometri
a 5
256
Un
729
2
r
3
Sn
Jeff Bivin -- LZHS
5
a U nr
Sn
1 r
Sn
512
2187
1
3
256 2
5
729 3
2
1
3
10423
Sn
729
10
Hitunglah 2 = 2 + 4 + 8+…+1024
k
k 1
a=2
r=2
n = 10
Un = 1024
Jeff Bivin -- LZHS
a ar
Sn
1 r
10
2 22
Sn
1 2
2 2 1024
Sn
1
2046
Sn
2046
1
n
8
Hitunglah 3 2 = 3 + 6 + 12 +…+ 384
j 1
j 1
a ar
Sn
1 r
8
3 3 2
Sn
1 2
3 3 256
Sn
1
765
Sn
765
1
n
a=3
r=2
n=8
Un = 384
Jeff Bivin -- LZHS
Rangkuman -- Geometri
Rumus
Suku-n
Un =
(n-1)
a·r
Jumlah Suku-n
a ar
Sn
1 r
n
a U nr
Sn
1 r
Jeff Bivin -- LZHS
Deret Geometri Tak Hingga
Jeff Bivin -- LZHS
The Magic Flea
(magnified for easier viewing)
Jeff Bivin -- LZHS
There is
no flea
like a
Magic
Flea
The Magic Flea
(magnified for easier viewing)
...
1 1
32 16
1
8
1
4
1
2
1 1 1
1
1
S
... 1
2 4 8 16 32
Jeff Bivin -- LZHS
Jumlah Deret Geometri
Tak Hingga
S
ar
i 1
untuk
Jeff Bivin -- LZHS
n 1
a
1 r
r 1
Ingat --The Magic Flea
1 1 1
1
1
S
... 1
2 4 8 16 32
a
S
1 r
1
a 12
2
S
1
1
1
r 2
2
S
Jeff Bivin -- LZHS
1
2
1
2
1
2 2
2
S 6 2
...
3 9 27
a
S
a 6
1 r
1
6
r
S
3
1 1
3
S
Jeff Bivin -- LZHS
6
2
3
9
A Bouncing Ball
rebounds ½ of the distance from which it fell -What is the total vertical distance that the
ball traveled before coming to rest if it fell
from the top of a 128 feet tall building?
Jeff Bivin -- LZHS
A Bouncing Ball
Lintasan Turun
= 128 + 64 + 32 + 16 + 8 + …
a
128 128
S
256
1
1 r 1 12
2
Jeff Bivin -- LZHS
A Bouncing Ball
Lintasan Naik = 64 + 32 + 16 + 8 + …
a
64
64
S
128
1
1 r 1 12
2
Jeff Bivin -- LZHS
A Bouncing Ball
L Turun = 128 + 64 + 32 + 16 + 8 + … = 256
L Naik =
64 + 32 + 16 + 8 + … = 128
TOTAL = 384 ft.
Jeff Bivin -- LZHS
A Bouncing Ball
rebounds 3/5 of the distance from which it fell -What is the total vertical distance that the ball
traveled before coming to rest if it fell from the top
of a 625 feet tall building?
Jeff Bivin -- LZHS
A Bouncing Ball
L Turun
= 625 + 375 + 225 + 135 + 81 + …
a
625 625
S
1562
.
5
3
2
1 r 1 5
5
Jeff Bivin -- LZHS
A Bouncing Ball
L Naik
= 375 + 225 + 135 + 81 + …
a
375 375
S
937
.
5
2
1 r 1 53
5
Jeff Bivin -- LZHS
A Bouncing Ball
L Turun = 625 + 375 + 225 + 135 + 81 + … = 1562.5
L Naik =
375 + 225 + 135 + 81 + … = 937.5
TOTAL = 2500 ft.
Jeff Bivin -- LZHS
Menentukan jumlah tak hingga
Sn .9 .09 .009 .0009 .00009 ...
a .9
r .1
Jeff Bivin -- LZHS
a
S
1 r
.9
S
1 .1
.9
S
1
.9
Pecahan – Desimal Tak hingga
.1
Jeff Bivin -- LZHS
1
9
.2
2
9
.3
3
9
.4
4
9
.5
5
9
1
3
.6
6
9
.7
7
9
.8
8
9
.9
9
9
2
3
1
Mari kita coba kembali
.3
.3
.3
.9
Jeff Bivin -- LZHS
1
3
1
3
1
3
3
1
3
Keunikan
let
subtract
Jeff Bivin -- LZHS
10 x 9. 9
x .9
9x 9
9
x 9 1
OK now a series
. 9 .9 .09 .009 .0009 .00009 ...
a1 .9
r .1
a1
S
1 r
.9
S
1 .1
.9
. 9 S
1
.9
Jeff Bivin -- LZHS
.9 = 1
That’s All
Folks
.9 1
Jeff Bivin -- LZHS
.9 = 1