Step 1: Understanding the Concept:
The derivative $f'(x)$ represents the slope of the function. The sign of the slope tells us the behavior of the function (increasing or decreasing). Step 2: Detailed Explanation:
If $f'(x)>0$, the slope is "upward," meaning the function is increasing.
If $f'(x)<0$, the slope is "downward," meaning the function is decreasing.
If $f'(x) = 0$, the function is at a stationary point (like a peak or valley).