Mathematics
Grade 12
15 min
Average rate of change
Average rate of change
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1
Introduction & Learning Objectives
Learning Objectives
Define the average rate of change in the context of functions.
Calculate the average rate of change of a function given its equation over a specified interval.
Determine the average rate of change from a table of values or a graph.
Interpret the meaning of the average rate of change in real-world scenarios.
Connect the average rate of change to the geometric concept of a secant line's slope.
Distinguish between the average rate of change over an interval and the instantaneous rate of change at a point.
Ever wonder what your average speed was on a road trip, even though your speedometer was constantly changing? 🚗 That's the average rate of change in action!
This tutorial will explore the average rate of change, a fundamental concept that measur...
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Key Concepts & Vocabulary
TermDefinitionExample
IntervalA continuous range of numbers between two endpoints. For average rate of change, we consider a closed interval, denoted as [a, b], which includes the endpoints a and b.The interval [1, 5] represents all real numbers from 1 to 5, including 1 and 5.
Change in y (Δy)The total vertical change, or the difference in the function's output values, between the two endpoints of an interval.For the function f(x) = x^2 on the interval [2, 5], Δy = f(5) - f(2) = 5^2 - 2^2 = 25 - 4 = 21.
Change in x (Δx)The total horizontal change, or the difference in the function's input values, which is simply the length of the interval.For the interval [2, 5], Δx = 5 - 2 = 3.
Secant LineA straight line that passes through two distinct points on the curve of a function.For f(x...
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Core Formulas
The Average Rate of Change Formula
AROC = \frac{\Delta y}{\Delta x} = \frac{f(b) - f(a)}{b - a}
This is the primary formula used to calculate the average rate of change of a function f(x) over the closed interval [a, b]. It is identical to the slope formula for a line passing through the points (a, f(a)) and (b, f(b)).
The Difference Quotient
AROC = \frac{f(x+h) - f(x)}{h}
This is an alternative form of the AROC formula, where the interval is defined from x to x+h, and the length of the interval is h. This form is crucial for understanding the definition of the derivative, where we find the limit as h approaches 0.
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Challenging
Find the simplified average rate of change of the function f(x) = 1/(x-2) on the interval [a, a+h].
A.-1 / ((a+h-2)(a-2))
B.1 / ((a+h-2)(a-2))
C.h / ((a+h-2)(a-2))
D.-h
Challenging
For which of the following types of functions is the average rate of change constant for any chosen interval [a, b] (where a ≠b)?
A.Quadratic functions (f(x) = ax^2 + bx + c)
B.Exponential functions (f(x) = a^x)
C.Linear functions (f(x) = mx + c)
D.Cubic functions (f(x) = ax^3 + ...)
Challenging
Find the average rate of change on the interval [1, 4] for the piecewise function defined as:
f(x) = x^2, if x ≤ 2
f(x) = 3x - 2, if x > 2
A.9
B.3
C.7/3
D.4
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