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Ch. 4 - Applications of Derivatives
Hass - Thomas' Calculus 15th Edition
Hass15th EditionThomas' CalculusISBN: 9780137616077Not the one you use?Change textbook
Chapter 4, Problem 4.1.7

Finding Extrema from Graphs


In Exercises 7–10, find the absolute extreme values and where they occur.


Graph showing points and lines indicating local extrema on a coordinate plane with labeled axes.

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First, identify the endpoints of the graph. The graph has endpoints at (-1, 1) and (1, -1). These points are important because absolute extrema can occur at endpoints.
Next, observe the graph to identify any local extrema. Local extrema are points where the graph changes direction. In this graph, there is a local maximum at (0, 0) because the graph changes from increasing to decreasing.
Determine the y-values at the endpoints and the local extrema. At (-1, 1), the y-value is 1; at (0, 0), the y-value is 0; and at (1, -1), the y-value is -1.
Compare the y-values to find the absolute maximum and minimum. The absolute maximum is the highest y-value, which is 1 at (-1, 1). The absolute minimum is the lowest y-value, which is -1 at (1, -1).
Conclude that the absolute maximum value is 1 occurring at x = -1, and the absolute minimum value is -1 occurring at x = 1.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Absolute Extrema

Absolute extrema refer to the highest or lowest points on a graph over a given interval. The absolute maximum is the highest point, while the absolute minimum is the lowest. These points can occur at critical points or endpoints of the interval. Identifying these points involves evaluating the function at critical points and endpoints to determine the largest and smallest values.
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Critical Points

Critical points are where the derivative of a function is zero or undefined, indicating potential local maxima, minima, or points of inflection. To find these points, take the derivative of the function and solve for where it equals zero or is undefined. These points are essential in determining where the function's slope changes, which helps in identifying extrema.
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Graph Analysis

Graph analysis involves examining a graph to identify key features such as intercepts, slopes, and extrema. By analyzing the graph, one can visually determine where the function reaches its highest or lowest values. This process includes observing the behavior of the graph at endpoints and critical points, which is crucial for finding absolute extrema.
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