6. Let p be a prime number and k an integer such that x 2 + kx + p = 0 has two positive integer solutions. What is the value of k+ p? 1 O -1 O 2 O -2
6. Let p be a prime number and k an integer such that x 2 + kx + p = 0 has two positive integer solutions. What is the value of k+ p? 1 O -1 O 2 O -2
Advanced Engineering Mathematics
10th Edition
ISBN:9780470458365
Author:Erwin Kreyszig
Publisher:Erwin Kreyszig
Chapter2: Second-order Linear Odes
Section: Chapter Questions
Problem 1RQ
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![**Question 6: Quadratic Equation Problem**
Let \( p \) be a prime number and \( k \) an integer such that the quadratic equation \( x^2 + kx + p = 0 \) has two positive integer solutions. What is the value of \( k + p \)?
**Options:**
- ○ 1
- ○ -1
- ○ 0
- ○ 2
- ○ -2
**Solution Explanation:**
To solve this problem, we determine the conditions under which the quadratic equation has two positive integer solutions. The roots of the equation are solutions to:
\[ x^2 + kx + p = 0 \]
Using Vieta’s formulas, if the roots are \( r_1 \) and \( r_2 \), then:
1. The sum of the roots \( r_1 + r_2 = -k \)
2. The product of the roots \( r_1 \cdot r_2 = p \)
Since \( r_1 \) and \( r_2 \) are positive integers, and \( p \) is a prime number, the only possible values for \( r_1 \) and \( r_2 \) are \( 1 \) and \( p \), giving us:
\[ r_1 = 1, \, r_2 = p \quad \text{or} \quad r_1 = p, \, r_2 = 1 \]
In both scenarios, \( r_1 + r_2 = 1 + p \).
Thus:
\[ -k = 1 + p \Rightarrow k = -(1 + p) \]
To find \( k + p \):
\[ k + p = -(1 + p) + p = -1 \]
Hence, the correct answer is \(-1\).](/v2/_next/image?url=https%3A%2F%2Fcontent.bartleby.com%2Fqna-images%2Fquestion%2Fadf70025-15e9-4d93-968e-9d86049b61bd%2F5f77f3a0-900f-4a21-803d-8329c8141079%2F2ridp4_processed.jpeg&w=3840&q=75)
Transcribed Image Text:**Question 6: Quadratic Equation Problem**
Let \( p \) be a prime number and \( k \) an integer such that the quadratic equation \( x^2 + kx + p = 0 \) has two positive integer solutions. What is the value of \( k + p \)?
**Options:**
- ○ 1
- ○ -1
- ○ 0
- ○ 2
- ○ -2
**Solution Explanation:**
To solve this problem, we determine the conditions under which the quadratic equation has two positive integer solutions. The roots of the equation are solutions to:
\[ x^2 + kx + p = 0 \]
Using Vieta’s formulas, if the roots are \( r_1 \) and \( r_2 \), then:
1. The sum of the roots \( r_1 + r_2 = -k \)
2. The product of the roots \( r_1 \cdot r_2 = p \)
Since \( r_1 \) and \( r_2 \) are positive integers, and \( p \) is a prime number, the only possible values for \( r_1 \) and \( r_2 \) are \( 1 \) and \( p \), giving us:
\[ r_1 = 1, \, r_2 = p \quad \text{or} \quad r_1 = p, \, r_2 = 1 \]
In both scenarios, \( r_1 + r_2 = 1 + p \).
Thus:
\[ -k = 1 + p \Rightarrow k = -(1 + p) \]
To find \( k + p \):
\[ k + p = -(1 + p) + p = -1 \]
Hence, the correct answer is \(-1\).
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