Question
Find (A) the leading term of the polynomial, (B) the limit as \( x \) approaches \( \infty \), and (C) the limit as \( x \) approaches \( -\infty \). \( p(x)=18+2 x^{6}-5 x^{7} \) (A) The leading term is \( -5 x^{7} \). (B) The limit of \( p(x) \) as \( x \) approaches \( \infty \) is \( \square \).
Ask by Cook Adkins. in the United States
Jan 22,2025
Real Tutor Solution
Tutor-Verified Answer
Answer
(A) The leading term is \( -5x^{7} \).
(B) The limit of \( p(x) \) as \( x \) approaches \( \infty \) is \( -\infty \).
(C) The limit of \( p(x) \) as \( x \) approaches \( -\infty \) is \( +\infty \).
Solution
Certainly! Let's analyze the polynomial \( p(x) = 18 + 2x^{6} - 5x^{7} \) step by step.
### (A) Leading Term
The **leading term** of a polynomial is the term with the highest degree (the largest exponent of \( x \)).
For \( p(x) = 18 + 2x^{6} - 5x^{7} \):
- The degrees of the terms are:
- \( 18 \) has degree 0.
- \( 2x^{6} \) has degree 6.
- \( -5x^{7} \) has degree 7.
**Leading Term:** \( -5x^{7} \)
---
### (B) Limit as \( x \) Approaches \( \infty \)
To find \( \lim_{x \to \infty} p(x) \), we consider the behavior of the leading term since it dominates the polynomial for large \( x \).
- **Leading Term:** \( -5x^{7} \)
As \( x \to \infty \):
- \( x^{7} \) grows without bound towards \( +\infty \).
- Multiplying by \( -5 \), the term \( -5x^{7} \) tends to \( -\infty \).
**Limit:**
\[
\lim_{x \to \infty} p(x) = -\infty
\]
---
### (C) Limit as \( x \) Approaches \( -\infty \)
Similarly, to find \( \lim_{x \to -\infty} p(x) \), we analyze the leading term.
- **Leading Term:** \( -5x^{7} \)
As \( x \to -\infty \):
- For odd exponents, \( x^{7} \) behaves as \( x \) does. So, \( x^{7} \) tends to \( -\infty \).
- Multiplying by \( -5 \), the term \( -5x^{7} \) tends to \( +\infty \).
**Limit:**
\[
\lim_{x \to -\infty} p(x) = +\infty
\]
---
### Summary
- **(A)** The leading term is \( -5x^{7} \).
- **(B)** \( \lim_{x \to \infty} p(x) = -\infty \).
- **(C)** \( \lim_{x \to -\infty} p(x) = +\infty \).
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Bonus Knowledge
As \( x \) approaches \( \infty \), the leading term of the polynomial \( p(x) = 18 + 2x^6 - 5x^7 \) dominates. Since the leading term is \( -5x^7 \), the limit will also be determined by this term. Therefore, the limit of \( p(x) \) as \( x \) approaches \( \infty \) is \( -\infty \). Now, as \( x \) approaches \( -\infty \), the leading term \( -5x^7 \) will go to \( +\infty \) since the power \( 7 \) is odd and the coefficient is negative. Therefore, the limit of \( p(x) \) as \( x \) approaches \( -\infty \) is \( \infty \).