multiple - choice question\nfor the function f, lim(x→ - ∞) f(x) = ∞ and lim(x→+∞) f(x)= - ∞, which of the…

multiple - choice question\nfor the function f, lim(x→ - ∞) f(x) = ∞ and lim(x→+∞) f(x)= - ∞, which of the following must be true about f?\nthe degree of f is even, and the leading coefficient is negative.\nthe degree of f is odd, and the leading coefficient is negative.\nthe degree of f is odd, and the leading coefficient is positive.\nthe degree of f is even, and the leading coefficient is positive.
Answer
Explanation:
Step1: Recall end - behavior rules
For a polynomial function $f(x)=a_nx^n + a_{n - 1}x^{n-1}+\cdots+a_0$, the end - behavior is determined by the degree $n$ and the leading coefficient $a_n$.
Step2: Analyze cases for different degrees and leading coefficients
If $n$ is even: $\lim_{x\rightarrow-\infty}f(x)=\lim_{x\rightarrow\infty}f(x)$ (both $\infty$ or both $-\infty$) depending on the sign of $a_n$. If $n$ is odd: $\lim_{x\rightarrow-\infty}f(x)=-\lim_{x\rightarrow\infty}f(x)$. Given $\lim_{x\rightarrow-\infty}f(x)=\infty$ and $\lim_{x\rightarrow\infty}f(x)=-\infty$, the degree $n$ must be odd. When $n$ is odd and $a_n<0$, $\lim_{x\rightarrow-\infty}f(x)=\infty$ and $\lim_{x\rightarrow\infty}f(x)=-\infty$.
Answer:
The degree of $f$ is odd, and the leading coefficient is negative.