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Ayen Dueños Mod 7 Activity 6 Think Think and Lost

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Name: Ayen Dueños

Section: Biotechnology

Directions: SHOW YOUR SOLUTIONS. BOX YOUR FINAL ANSWER.

1 1
1. −4, −1 , 1, 3 , 6, …
2 2

a. 𝒂𝟏 = −𝟒

𝑎2 − 𝑎1 = 𝑎4 − 𝑎3 1
𝑎20 = −4 + (20 − 1)2
1 1 2
−1 − (−4) = 3 − 1 1
2 2 𝑎20 = −4 + (19)2
2
1 1
2 =2 𝑎20 = −4 + 47.5
2 2
𝒂𝟐𝟎 = 𝟒𝟑. 𝟓
𝟏
𝒅=𝟐
𝟐
𝑛
𝑏. 𝑎𝑛 + (𝑛 − 1)𝑑 𝑐. 𝑆𝑛 = [2𝑎1 + (𝑛 − 1)𝑑]
1 2
41 = −4 + (𝑛 − 1)2 84
2 𝑆84 = [2(1) + (84 − 1)2.5]
1 1 2
41 = −4 + 2 𝑛 − 2
2 2 𝑆84 = 42 [2 + (83)2.5]
1 1
41 = 2 𝑛 − 6 𝑆84 = 42 [2 + (207.5)]
2 2
1 1 𝑆84 = 42 (209.5)
41 + 6 = 2 𝑛
2 2 𝑆84 = 8799
1
47.5 = 2 𝑛 8799 is the sum of the
2
41 is in the 19th term first 84 positive integers
𝑛 = 19

32
2. 24, 16, ,…
3
𝑎1 (𝑟 𝑛 − 1)
𝑎2 𝑎3 𝑏. 𝑎𝑛 = 𝑎1 𝑟 𝑛−1 𝑐. 𝑆𝑛 =
𝑟−1 𝑑. 𝑎𝑛 = 𝑎1 𝑟 𝑛−1
𝑎. =
𝑎1 𝑎2 2 2
6
𝑎6 = 24( )6−1 24 ቆ൬ ൰ − 1ቇ 1024 2
3 3 = 24( )𝑛−1
32 𝑆6 = 729 3
16 3 32 2
= 𝑎6 = 24( ) −1
243 3 6561
24 16 𝑖𝑛 2 ∙ 𝑖𝑛 ൬ ൰
64
24 ൬( ) − 1൰
128
𝟐𝟓𝟔 729 𝑛=
𝟐 𝟐 𝒂𝟔 = 𝑆6 = 𝑖𝑛(2) − 𝑖𝑛3
= 𝟖𝟏 2
𝟑 𝟑 −1
3
−21.893 𝒏=𝟖
𝑆6 =
−0.3333

𝑺𝟔 = 𝟔𝟓. 𝟕

1 1 1 The given series don’t have a sum because the formula in


3. , , ,…
128 64 32 getting the infinite geometric series is being applied only
when │r│< 1. In this series, the ratio is equal to 2, which is
greater than 1.

𝑎1
1−𝑟 (1 − 𝑟 𝑛 )
4. 5. 𝑆6 = 𝑎1
1 1−𝑟
1 − (− ) 1 6
3 2 1 − ൬2൰
81 𝑆6 =
3 1
= 2
1
1 1
3 2 1 −
64
𝑆6 =
81 3 1
= 2
4 63
3 2 64
𝑆6 =
3 1
81 3 243 2
= ∗ = 21
21 2 21
1 4 4 32 𝑆6 = ∗ =
𝑆6 = 32 1 16
1
𝟑 2
= 𝟔𝟎 𝟓 1 5/6 or 1.3125 is the sum of
𝟒 𝑺𝟔 = 𝟏
𝟏𝟔 the first 6 terms.

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