Respuesta :
A geometric sequence is characterized with a common ratio
- [tex]\mathbf{r = \frac{1}{3}\ and\ \mathbf{n = 36, 12, 4}}[/tex] ,
- [tex]\mathbf{r = -4 \ and\ n = 192, -768, 3072}[/tex],
- [tex]\mathbf{r = 5 \ and\ n = 12.5, 62.5, 312.5}[/tex],
- [tex]\mathbf{r = \frac{1}{10} \ and\ n = 10, 1, \frac{1}{10}}[/tex],
- [tex]\mathbf{r = -1 \ and\ n = 4,-4,4}[/tex],
- [tex]\mathbf{n = 2, 8}[/tex],
- [tex]\mathbf{n = 5, -\frac 53}[/tex],
- [tex]\mathbf{a_7 = 46875}[/tex],
- [tex]\mathbf{a_{30} = 0}[/tex],
- 64 is 7th term
The common ratio and the next three terms
Given the first three terms, the common ratio (r) is:
[tex]\mathbf{r = \frac{T_2}{T_1}}[/tex]
While the nth term is:
[tex]\mathbf{T_n = T_1 \times r^{n-1}}[/tex]
So, we have:
1. 972, 324, 108, …
The common ratio (r) is:
[tex]\mathbf{r = \frac{324}{972}}[/tex]
[tex]\mathbf{r = \frac{1}{3}}[/tex]
The next three terms are:
[tex]\mathbf{T_4 = 972 \times (\frac 13)^3 = 36}[/tex]
[tex]\mathbf{T_5 = 972 \times (\frac 13)^4 = 12}[/tex]
[tex]\mathbf{T_6 = 972 \times (\frac 13)^5 = 4}[/tex]
So,
[tex]\mathbf{r = \frac{1}{3}\ and\ \mathbf{n = 36, 12, 4}}[/tex]
2. -3, 12, -48, …
The common ratio (r) is:
[tex]\mathbf{r = \frac{12}{-3}}[/tex]
[tex]\mathbf{r = -4}[/tex]
The next three terms are:
[tex]\mathbf{T_4 = -3 \times (-4)^3 = 192}[/tex]
[tex]\mathbf{T_5 = -3 \times (-4)^4 = -768}[/tex]
[tex]\mathbf{T_6 = -3 \times (-4)^5 = 3072}[/tex]
So,
[tex]\mathbf{r = -4 \ and\ n = 192, -768, 3072}[/tex]
3. 0.1, 0.5, 2.5, …
The common ratio (r) is:
[tex]\mathbf{r = \frac{0.5}{0.1}}[/tex]
[tex]\mathbf{r = 5}[/tex]
The next three terms are:
[tex]\mathbf{T_4 = 0.1 \times (5)^3 = 12.5}[/tex]
[tex]\mathbf{T_5 = 0.1 \times (5)^4 = 62.5}[/tex]
[tex]\mathbf{T_6 = 0.1 \times (5)^5 = 312.5}[/tex]
So,
[tex]\mathbf{r = 5 \ and\ n = 12.5, 62.5, 312.5}[/tex]
4. 10 000, 1 000, 100, …
The common ratio (r) is:
[tex]\mathbf{r = \frac{1000}{10000}}[/tex]
[tex]\mathbf{r = \frac{1}{10}}[/tex]
The next three terms are:
[tex]\mathbf{T_4 = 10000 \times (\frac{1}{10})^3 = 10}[/tex]
[tex]\mathbf{T_5 = 10000 \times (\frac{1}{10})^4 = 1}[/tex]
[tex]\mathbf{T_6 = 10000 \times (\frac{1}{10})^5 = \frac{1}{10}}[/tex]
So,
[tex]\mathbf{r = \frac{1}{10} \ and\ n = 10, 1, \frac{1}{10}}[/tex]
5. -4, 4, -4, ...
The common ratio (r) is:
[tex]\mathbf{r = \frac{4}{-4}}[/tex]
[tex]\mathbf{r = -1}[/tex]
The next three terms are:
[tex]\mathbf{T_4 = -4 \times (-1)^3 = 4}[/tex]
[tex]\mathbf{T_5 = -4 \times (-1)^4 = -4}[/tex]
[tex]\mathbf{T_6 = -4 \times (-1)^5 = 4}[/tex]
So,
[tex]\mathbf{r = -1 \ and\ n = 4,-4,4}[/tex]
The first 2 terms
[tex]6.\ \mathbf{a_1 =2 , r = 4}[/tex]
The nth term is:
[tex]\mathbf{a_n = a_1 \times r^{n-1}}[/tex]
So, the second term is:
[tex]\mathbf{a_2 = 2 \times 4 = 8}[/tex]
So, we have:
[tex]\mathbf{n = 2, 8}[/tex]
[tex]7.\ \mathbf{a_1 =5, r = -\frac 13}[/tex]
The nth term is:
[tex]\mathbf{a_n = a_1 \times r^{n-1}}[/tex]
So, the second term is:
[tex]\mathbf{a_2 = 5 \times -\frac 13 = -\frac 53}[/tex]
So, we have:
[tex]\mathbf{n = 5, -\frac 53}[/tex]
The nth term
[tex]\mathbf{8.\ a_1 = 3, r = 5}[/tex]
The 7th is calculated using:
[tex]\mathbf{a_7 = a_1 \times r^6}[/tex]
[tex]\mathbf{a_{7} = 3 \times 5^{6}}[/tex]
[tex]\mathbf{a_7 = 46875}[/tex]
[tex]\mathbf{9.\ a_1 = 0, r = 4}[/tex]
The 30th is calculated using:
[tex]\mathbf{a_{30} = a_1 \times r^{29}}[/tex]
[tex]\mathbf{a_{30} = 0 \times 4^{29}}[/tex]
[tex]\mathbf{a_{30} = 0}[/tex]
The number of term
[tex]\mathbf{10.\ n = 1,2,4,8....}[/tex]
[tex]\mathbf{a_n = 64}[/tex]
[tex]\mathbf{a_1 = 1}[/tex]
Start by calculating the common ratio (r)
[tex]\mathbf{r = \frac 21}[/tex]
[tex]\mathbf{r = 2}[/tex]
So, the nth term is:
[tex]\mathbf{a_n = a_1 \times r^{n-1}}[/tex]
Substitute known values
[tex]\mathbf{64 = 1 \times 2^{n-1}}[/tex]
[tex]\mathbf{64 = 2^{n-1}}[/tex]
Express 64 as 2^6
[tex]\mathbf{2^6 = 2^{n-1}}[/tex]
Cancel out 2 on both sides
[tex]\mathbf{6 = n-1}[/tex]
Add 1 to both sides
[tex]\mathbf{7 = n}[/tex]
Rewrite as:
[tex]\mathbf{n = 7}[/tex]
Hence:
64 is 7th term
Read more about geometric sequence at:
https://brainly.com/question/18109692