The graph depicts a linear function with a negative slope, meaning it is decreasing over its entire domain. For a linear function with a constant negative slope, the function decreases from $x = -\infty$ to $x = \infty$.

Answer:

The interval in which the function is decreasing is: $(-\infty, \infty)$

Would you like further details on this concept or have any questions?

Here are some related questions you might find helpful:

1. How do we determine intervals of increase or decrease for different types of functions?
2. What does it mean for a function to be increasing or decreasing on an interval?
3. How can we identify the slope of a linear function from its graph?
4. What are the characteristics of a linear function with a positive slope?
5. How does the behavior of a function differ between linear and nonlinear functions in terms of increasing and decreasing intervals?

Tip: For a function represented by a straight line, check the slope to determine if it’s increasing or decreasing; a positive slope means it increases, and a negative slope means it decreases.