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Ch. 1 - Functions
Hass - Thomas' Calculus 15th Edition
Hass15th EditionThomas' CalculusISBN: 9780137616077당신이 사용하는 게 아니라요?교과서 변경
1장, 문제 1.1.23a

Functions and Graphs


Graph the following equations and explain why they are not graphs of functions of x.


a. |y| = x

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First, understand the equation |y| = x. This equation involves the absolute value of y, which means y can be either positive or negative for each value of x.
To graph this equation, consider two separate cases: y = x and y = -x. These represent the two possible values of y for each x.
Graph the line y = x. This is a straight line passing through the origin with a slope of 1, meaning it rises one unit for every unit it moves to the right.
Graph the line y = -x. This is another straight line passing through the origin, but with a slope of -1, meaning it falls one unit for every unit it moves to the right.
Notice that for each x-value, there are two corresponding y-values (one positive and one negative). This violates the definition of a function, which requires each x-value to have exactly one y-value. Therefore, the graph is not a function of x.

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주요 개념

질문에 올바르게 답하기 위해 반드시 이해해야 하는 핵심 개념들은 다음과 같습니다.

Definition of a Function

A function is a relation that assigns exactly one output value for each input value. In mathematical terms, for a relation to be a function, it must pass the vertical line test, meaning that no vertical line intersects the graph of the relation at more than one point. This ensures that each input corresponds to a unique output.
추천 영상:
05:43
Definition of the Definite Integral

Vertical Line Test

The vertical line test is a method used to determine if a graph represents a function. If any vertical line drawn through the graph intersects it at more than one point, the graph does not represent a function. This test is crucial for identifying whether a given relation meets the criteria of a function.
추천 영상:
05:13
Slopes of Tangent Lines

Absolute Value Functions

An absolute value function, such as |y| = x, describes a relationship where the output is the non-negative value of the input. This specific equation implies that for each positive x, there are two corresponding y values (y and -y), which violates the definition of a function. Thus, it fails the vertical line test, indicating it is not a function of x.
추천 영상:
06:37
Average Value of a Function