Fonction décroissante

A decreasing function has outputs that get smaller as inputs increase. Mathematically, for any two input values where x1 < x2, the corresponding outputs satisfy f(x1) > f(x2). On a graph, this appears as a downward slope from left to right, visually confirming the declining relationship between input and output.

A decreasing function is identified by observing whether the graph slopes downward from left to right. As you move along the x-axis from left to right, the f(x)-values consistently get smaller. This visual pattern on a graphs of functions clearly indicates the function is decreasing across that interval.

A negative rate of change indicates a decreasing function. The average rate of change is calculated by dividing the change in output by the change in input. When this ratio is negative across intervals, the function is decreasing, meaning outputs decline as inputs increase.

For continuous functions, the derivative f′(x) serves as an indicator of whether a function is decreasing. If f′(x) < 0 for all x in an interval, the function is decreasing on that interval. A negative derivative confirms that outputs are declining as inputs increase.

Decreasing functions model many natural and technological phenomena where outputs decline with increasing input. Examples include the temperature of a cooling object, the voltage of a discharging battery, and the height of a falling object after its peak. These scenarios involve quantities that reduce as time or another input progresses.

Speed changes are calculated by determining the average rate of change between intervals. Divide the change in distance by the change in time between two recorded points to find average speed. Comparing speeds across successive intervals reveals whether the rate is increasing or decreasing over time.

A decreasing function has outputs that get smaller as inputs increase, while an increasing function has outputs that get larger. On a graph, a decreasing function slopes downward from left to right, whereas an increasing function slopes upward. Understanding both types helps analyze how quantities change across different intervals.