AP Calculus AB: 8.2.4 The First Derivative Test
This flashcard set explains how to use the First Derivative Test to identify relative maxima, minima, or neither at critical points. By analyzing the sign of the derivative on either side of a critical point, one can determine whether the function is increasing or decreasing, and thus classify the behavior of the function at that point.
The First Derivative Test
Determining the sign of the derivative immediately to either side of a critical point reveals whether that point is a relative maximum, relative minimum, or neither.
• The first derivative test states that if c is a critical point of f, and f is continuous and differentiable on an open interval containing c (except possibly at c), then f(c) can be classified as follows:
1) If f (c) < 0 for x < c and f (c) > 0 for x > c, then f(c) is a relative minimum of f.
2) If f (c) > 0 for x < c and f (c) < 0 for x > c, then f(c) is a relative maximum of f.
• On an interval, the sign of the first derivative of a function indicates whether that function is increasing or decreasing.
Key Terms
The First Derivative Test
Determining the sign of the derivative immediately to either side of a critical point reveals whether that point is a relative maximum, rel...
note
Maximum and minimum values of a function will only occur at critical points: places where the derivative is zero or undefined.
- ...
Suppose f (x) is continuous and defined for all real numbers. You are given that f (x) has critical points at x = −1 and x = 0. If f ′(x) is positive in the interval x < −1, negative in the interval −1 < x < 0, and positive in the interval x > 0, is the point where x = 0 the location of a relative maximum, minimum, or neither?
Minimum
Suppose g(x)is continuous and defined for all real numbers. You are given that g(x)has critical points at x=−5/2andx=−1. If g’(x)is positive in the interval x−1,is the point where x=−5/2 the location of a relative maximum, minimum, or neither?
Neither
Suppose that h (x) is a continuous function and is defined for all x greater than or equal to 1. You are given that h (x) has critical points at x = 1, x = 3, and x = 5. If h′ (x) is negative on the interval 1 < x < 3, positive on the interval 3 < x < 5, and positive on the interval x > 5, what can be said about the point (3, h (3))?
(3, h (3)) is an absolute minimum
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| Term | Definition |
|---|---|
The First Derivative Test |
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note |
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Suppose f (x) is continuous and defined for all real numbers. You are given that f (x) has critical points at x = −1 and x = 0. If f ′(x) is positive in the interval x < −1, negative in the interval −1 < x < 0, and positive in the interval x > 0, is the point where x = 0 the location of a relative maximum, minimum, or neither? | Minimum |
Suppose g(x)is continuous and defined for all real numbers. You are given that g(x)has critical points at x=−5/2andx=−1. If g’(x)is positive in the interval x−1,is the point where x=−5/2 the location of a relative maximum, minimum, or neither? | Neither |
Suppose that h (x) is a continuous function and is defined for all x greater than or equal to 1. You are given that h (x) has critical points at x = 1, x = 3, and x = 5. If h′ (x) is negative on the interval 1 < x < 3, positive on the interval 3 < x < 5, and positive on the interval x > 5, what can be said about the point (3, h (3))? | (3, h (3)) is an absolute minimum |