Which of the following statements is true about function roots?

A root of a function is defined as a value of the variable (often denoted as 'x') for which the function evaluates to zero. This means that when you substitute the root back into the function, the output will equal zero. This characteristic makes it fundamental in solving equations and understanding the behavior of graphs related to that function.

In practical terms, identifying the roots of a function aids in determining the x-intercepts of its graph, which are the points where the curve crosses the x-axis. These intersections provide important information in various contexts, including physics, engineering, and economics, where they often represent critical points like equilibrium states or thresholds.

The other statements do not accurately reflect the definition or significance of a root in the context of functions. For instance, roots can be positive, negative, or even complex numbers; they are not constrained to being always positive. Additionally, a root does not indicate where the curve will rise; rather, it shows where the curve intersects the x-axis. Finally, roots are very relevant in real-world applications, contradicting the idea that they are irrelevant. Thus, the correct understanding of a root directly points to the condition where the function equals zero.