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Ch. 4 - Inverse, Exponential, and Logarithmic Functions
Lial - College Algebra 13th Edition
Lial13th EditionCollege AlgebraISBN: 9780136881063당신이 사용하는 게 아니라요?교과서 변경
5장, 문제 20

Determine whether each function graphed or defined is one-to-one. y = -√(100 - x2)

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Recall that a function is one-to-one if and only if each output corresponds to exactly one input. This means the function passes the Horizontal Line Test: no horizontal line intersects the graph more than once.
Examine the given function: \(y = -\sqrt{100 - x^2}\). Notice that the expression under the square root, \(100 - x^2\), represents a semicircle of radius 10 centered at the origin.
Since the square root function outputs only non-negative values, and there is a negative sign in front, \(y\) will be non-positive (zero or negative). This means the graph is the lower semicircle of the circle \(x^2 + y^2 = 100\).
Consider the symmetry of the semicircle: for a given \(y\) value (except the lowest point), there are two corresponding \(x\) values (one positive and one negative). This implies the function is not one-to-one because multiple \(x\) values produce the same \(y\) value.
Conclude that the function \(y = -\sqrt{100 - x^2}\) is not one-to-one because it fails the Horizontal Line Test due to the semicircular shape of its graph.

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주요 개념

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

One-to-One Function

A function is one-to-one if each output corresponds to exactly one input, meaning no two different inputs produce the same output. This property ensures the function has an inverse. To test this, the Horizontal Line Test is often used on the graph.
추천 영상:
4:07
Decomposition of Functions

Domain and Range of Functions

The domain is the set of all possible input values (x-values), and the range is the set of all possible output values (y-values). Understanding the domain and range helps determine the behavior of the function and whether it can be one-to-one.
추천 영상:
4:22
Domain & Range of Transformed Functions

Square Root and Quadratic Functions

The function y = -√(100 - x²) involves a square root of a quadratic expression. The expression inside the root, 100 - x², restricts the domain to values where the radicand is non-negative. The negative sign affects the output values, influencing the function's graph and one-to-one nature.
추천 영상:
06:12
Solving Quadratic Equations by the Square Root Property