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Geometric. Sequences & Series. Geometric Sequences. 1, 2, 4, 8, 16, 32, … 2 n-1 , … 3, 9, 27, 81, 243, … 3 n , . . . 81, 54, 36, 24, 16, … ,. n th term of geometric sequence. a n = a 1 ·r (n-1). Find the n th term of the geometric sequence. First term is 2
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Geometric Sequences & Series
Geometric Sequences 1, 2, 4, 8, 16, 32, … 2n-1, … 3, 9, 27, 81, 243, … 3n, . . . 81, 54, 36, 24, 16, … , . . .
nth term of geometric sequence an = a1·r(n-1)
Find the nth term of thegeometric sequence First term is 2 Common ratio is 3 an = a1·r(n-1) an = 2(3)(n-1)
EX1 Find the nth term of a geometric sequence a) First term is 128 Common ratio is (1/2) an = a1·r(n-1)
Ex 1 Find the nth term of the geometric sequence b) First term is 64 Common ratio is (3/2) an = a1·r(n-1)
c) Finding the 10th term a1 = 3 r = 2 n = 10 3, 6, 12, 24, 48, . . . an = a1·r(n-1) an = 3·(2)10-1 an = 3·(2)9 an = 3·(512) an = 1536
d) Finding the 8th term a1 = 2 r = -5 n = 8 2, -10, 50, -250, 1250, . . . an = a1·r(n-1) an = 2·(-5)8-1 an = 2·(-5)7 an = 2·(-78125) an = -156250
1 + 3 + 9 + 27 + 81 + 243 a1 = 1 r = 3 n = 6
EX 2 Find the suma) 4 - 8 + 16 - 32 + 64 – 128 + 256 a1 = 4 r = -2 n = 7
b) Evaluate = 2 + 4 + 8+…+1024 a1 = 2 r = 2 n = 10
c) Evaluate = 3 + 6 + 12 +…+ 384 a1 = 3 r = 2 n = 8
Review -- Geometric Sum of n terms nth term an = a1·r(n-1)
Geometric Infinite Series
c) 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? 128 ft 64 ft 32 ft 16 ft 8 ft
A Bouncing Ball Downward = 128 + 64 + 32 + 16 + 8 + … 128 ft 64 ft 32 ft 16 ft 8 ft
A Bouncing Ball Upward = 64 + 32 + 16 + 8 + … 128 ft 64 ft 32 ft 16 ft 8 ft Jeff Bivin -- LZHS
A Bouncing Ball Downward = 128 + 64 + 32 + 16 + 8 + … = 256 Upward = 64 + 32 + 16 + 8 + … = 128 TOTAL = 384 ft. 128 ft 64 ft 32 ft 16 ft 8 ft
d) 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? 625 ft 375 ft 225 ft 135 ft 81 ft
A Bouncing Ball Downward = 625 + 375 + 225 + 135 + 81 + … 625 ft 375 ft 225 ft 135 ft 81 ft
A Bouncing Ball Upward = 375 + 225 + 135 + 81 + … 625 ft 375 ft 225 ft 135 ft 81 ft
A Bouncing Ball Downward = 625 + 375 + 225 + 135 + 81 + … = 1562.5 Upward = 375 + 225 + 135 + 81 + … = 937.5 TOTAL = 2500 ft. 625 ft 375 ft 225 ft 135 ft 81 ft