av David Kedrowski för 14 årar sedan
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Let f be a function such that f'(c) = 0 and the second derivative of f exists on an open interval containing c.
If f''(c) = 0, the test fails. That is, f may have a relative maximum, a relative minimum, or neither. In such cases, you can use the First Derivative Test.
If (c,f(c)) is a point of inflection of the graph of f, then either f''(c) = 0 or f'' does not exist at x = c.
Note: The converse is not, in general, true. For example, consider f(x) = x^4 at c = 0.
Let f be a function that is continuous on an open interval and let c be a point in the interval. If the graph of f has a tangent line at this point (c,f(c)), then this point is a point of inflection of the graph of f if the concavity of f changes from upward to downward (or downward to upward) at the point.
This definition is slightly more restrictive than is sometimes used in that it requires a tangent line to exist at c.
Let f be a function whose second derivative exists on an open interval I.
Let f be differentiable on an open interval I. The graph of f is concave upward on I if f' is increasing on the interval and concave downward on I if f' is decreasing on the interval.
Let c be a critical number of a function f that is continuous on an open interval I containing c. If f is differentiable on the interval, except possibly at c, then f(c) can be classified as follows.
Guidelines For Finding Intervals On Which A Function Is Increasing Or Decreasing
Let f be continuous on the interval (a,b). To find the open intervals on which f is increasing or decreasing, use the following steps.
These guidelines are also valid if the interval (a,b) is replaced by an interval of the form (-infinity,b), (a,infinity), or (-infinity,infinity).
Let f be a function that is continuous on the closed interval [a,b] and differentiable on the open interval (a,b).
The conclusions in the first two cases are valid even if f'(x) = 0 at a finite number of x-values in (a,b).
A function f is increasing on an interval if for any two numbers x_1 and x_2 in the interval, x_1 < x_2 implies f(x_1) < f(x_2).
A function f is decreasing on an interval if for any two numbers x_1 and x_2 in the interval, x_1 < x_2 implies f(x_1) > f(x_2).