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There is no integer value of \( n \) for which \( T_n = 24,\!977 \) in the given sequence.
Solución
Let's analyze the given number pattern and address each of your questions step-by-step.
## Given Sequence:
\[ 6; \, 13; \, 22; \, 33 \]
### 1.1. **Write Down the Next Terms of the Number Pattern**
To identify the pattern, let's examine the differences between consecutive terms:
\[
\begin{align*}
13 - 6 &= 7 \\
22 - 13 &= 9 \\
33 - 22 &= 11 \\
\end{align*}
\]
**Differences between terms:** \( 7, \, 9, \, 11 \)
We observe that the differences are increasing by **2** each time. Continuing this pattern:
\[
\begin{align*}
\text{Next difference} &= 11 + 2 = 13 \\
\text{Next term} &= 33 + 13 = 46 \\
\text{Following difference} &= 13 + 2 = 15 \\
\text{Next term} &= 46 + 15 = 61 \\
\text{And so on...} \\
\end{align*}
\]
**Next few terms of the sequence:** \( 46, \, 61, \, 78, \, \ldots \)
---
### 1.2. **Determine the \( n^{\text{th}} \) Term of the Sequence**
Since the differences between consecutive terms are increasing by a constant (2), the sequence is **quadratic**. The general form of a quadratic sequence is:
\[
T_n = an^2 + bn + c
\]
To find the coefficients \( a \), \( b \), and \( c \), we'll use the first three terms of the sequence.
**Given:**
\[
\begin{align*}
T_1 &= 6 \\
T_2 &= 13 \\
T_3 &= 22 \\
\end{align*}
\]
**Setting up the equations:**
\[
\begin{cases}
a(1)^2 + b(1) + c = 6 \quad \Rightarrow \quad a + b + c = 6 \quad \text{(1)} \\
a(2)^2 + b(2) + c = 13 \quad \Rightarrow \quad 4a + 2b + c = 13 \quad \text{(2)} \\
a(3)^2 + b(3) + c = 22 \quad \Rightarrow \quad 9a + 3b + c = 22 \quad \text{(3)} \\
\end{cases}
\]
**Solving the equations:**
1. Subtract equation (1) from equation (2):
\[
(4a + 2b + c) - (a + b + c) = 13 - 6 \\
\Rightarrow 3a + b = 7 \quad \text{(4)}
\]
2. Subtract equation (2) from equation (3):
\[
(9a + 3b + c) - (4a + 2b + c) = 22 - 13 \\
\Rightarrow 5a + b = 9 \quad \text{(5)}
\]
3. Subtract equation (4) from equation (5):
\[
(5a + b) - (3a + b) = 9 - 7 \\
\Rightarrow 2a = 2 \\
\Rightarrow a = 1
\]
4. Substitute \( a = 1 \) into equation (4):
\[
3(1) + b = 7 \\
\Rightarrow b = 4
\]
5. Substitute \( a = 1 \) and \( b = 4 \) into equation (1):
\[
1 + 4 + c = 6 \\
\Rightarrow c = 1
\]
**Therefore, the \( n^{\text{th}} \) term of the sequence is:**
\[
T_n = n^2 + 4n + 1
\]
**Verification:**
\[
\begin{align*}
T_1 &= 1^2 + 4(1) + 1 = 6 \\
T_2 &= 2^2 + 4(2) + 1 = 13 \\
T_3 &= 3^2 + 4(3) + 1 = 22 \\
T_4 &= 4^2 + 4(4) + 1 = 33 \\
\end{align*}
\]
All terms match the given sequence.
---
### 1.3. **For What Value of \( n \) is \( T_n = 24,\!977 \)?**
We need to solve for \( n \) in the equation:
\[
n^2 + 4n + 1 = 24,\!977
\]
**Step 1: Rearrange the Equation**
\[
n^2 + 4n + 1 - 24,\!977 = 0 \\
\Rightarrow n^2 + 4n - 24,\!976 = 0
\]
**Step 2: Use the Quadratic Formula**
The quadratic equation \( ax^2 + bx + c = 0 \) has solutions:
\[
n = \frac{-b \pm \sqrt{b^2 - 4ac}}{2a}
\]
Here, \( a = 1 \), \( b = 4 \), and \( c = -24,\!976 \).
\[
\begin{align*}
n &= \frac{-4 \pm \sqrt{4^2 - 4(1)(-24,\!976)}}{2(1)} \\
&= \frac{-4 \pm \sqrt{16 + 99,\!904}}{2} \\
&= \frac{-4 \pm \sqrt{99,\!920}}{2} \\
\end{align*}
\]
**Step 3: Calculate the Discriminant**
\[
\sqrt{99,\!920} \approx 316.1
\]
**Step 4: Find \( n \)**
\[
n = \frac{-4 \pm 316.1}{2}
\]
Since \( n \) must be a positive integer:
\[
n \approx \frac{-4 + 316.1}{2} \approx \frac{312.1}{2} \approx 156.05
\]
**Conclusion:**
Since \( n \) must be an integer, and the closest integer values are:
- \( n = 156 \):
\[
T_{156} = 156^2 + 4(156) + 1 = 24,\!336 + 624 + 1 = 24,\!961
\]
- \( n = 157 \):
\[
T_{157} = 157^2 + 4(157) + 1 = 24,\!649 + 628 + 1 = 25,\!278
\]
Neither \( T_{156} \) nor \( T_{157} \) equals 24,977. Thus:
**There is no integer value of \( n \) for which \( T_n = 24,\!977 \) in this sequence.**
Revisado y aprobado por el equipo de tutoría de UpStudy
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