Fundamental Ideas of “Change in Tandem”
Definition of a Function
A function is a specific type of relation between two sets, typically referred to as the domain (input values) and the range (output values). For each element in the domain, there is a unique corresponding element in the range. This unique correspondence ensures that for every input value, there is exactly one output value.
Covariation
Covariation refers to the way the output value of a function changes in response to changes in the input value. Understanding covariation is crucial for analyzing and interpreting the behavior of functions. It helps in understanding how variables associated with the function move in tandem with each other.
Synchronized Changes
“Change in Tandem” highlights how input and output values of a function vary together, following the rule defined by the function. This rule can be represented in various forms: graphically, numerically, analytically (using an equation), or verbally. These representations help in visualizing and understanding the nature of the change, whether it be linear, exponential, polynomial, etc.
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Applications and Implications
 Modeling RealWorld Situations: Many reallife phenomena can be modeled using functions, where understanding the synchronized changes between variables is key. For instance, determining how the distance traveled by a vehicle changes over time requires understanding how these variables change in tandem according to a specific rule or function.
 Increasing and Decreasing Functions: The concept of “Change in Tandem” also introduces the notion of functions being increasing or decreasing over certain intervals. A function is increasing if, as the input value increases, the output value also increases. Conversely, a function is decreasing if the output value decreases as the input value increases. This behavior is crucial for analyzing the growth or decay trends in various contexts.
 Graphical Interpretation: Graphically, “Change in Tandem” can be observed through the slope of the function on a coordinate plane. Positive slopes indicate increasing behavior, whereas negative slopes indicate decreasing behavior. This graphical perspective is vital for quickly assessing the behavior of functions over different intervals.