Answer:
Horizontal asymptote of y=1.
Explanation:
End behavior is talking about limits as x approaches infinity and negative infinity
![\lim_(x \to \infty) (x+1)/(x+3) = 1](https://img.qammunity.org/2021/formulas/mathematics/high-school/cqedwf5hy09m9w3eua906zhai4m3cec0tp.png)
because substituting large numbers in for x (like a million, billion, or trillion) would give basically a large number over basically the same large number, and anything over itself = 1.
![\lim_(x \to -\infty) (x+1)/(x+3) = 1](https://img.qammunity.org/2021/formulas/mathematics/high-school/181d1acuohrbjtzvbsp02hfahuj73fx8p8.png)
Same reasoning as the last one.
So, x+1/x+3 has a horizontal asymptote of y=1.