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Ch. 2 - Functions and Graphs
Blitzer - College Algebra 8th Edition
Blitzer8th EditionCollege AlgebraISBN: 9780136970514Non è quello che usi tu?Cambia libro di testo
Capitolo 3, Problema 14

In Exercises 11–26, determine whether each equation defines y as a function of x. x² + y = 25

Guida verificata passo dopo passo
1
Step 1: Recall the definition of a function. A relation defines y as a function of x if, for every value of x, there is exactly one corresponding value of y.
Step 2: Start with the given equation: x^2 + y = 25. Solve for y in terms of x by isolating y. Subtract x^2 from both sides to get y = 25 - x^2.
Step 3: Analyze the resulting equation y = 25 - x^2. For any given value of x, there is only one corresponding value of y because the equation does not involve any operations (like a square root) that could produce multiple outputs for the same input.
Step 4: Conclude that the equation y = 25 - x^2 defines y as a function of x because it passes the vertical line test. This means that for every x-value, there is exactly one y-value.
Step 5: Verify your conclusion by considering the graph of the equation. The graph of y = 25 - x^2 is a parabola that opens downward, and it satisfies the condition of being a function.

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Function Definition

A function is a relation between a set of inputs and a set of possible outputs where each input is related to exactly one output. In mathematical terms, for a relation to be a function, no two ordered pairs can have the same first element with different second elements. This concept is crucial for determining if an equation defines y as a function of x.
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Graphs of Common Functions

Vertical Line Test

The vertical line test is a visual way to determine if a curve is a graph of a function. If any vertical line intersects the graph at more than one point, then the graph does not represent a function. This test helps in analyzing equations to see if they can be expressed as y in terms of x.
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The Slope of a Line

Solving for y

To determine if an equation defines y as a function of x, it is often necessary to solve the equation for y. This involves isolating y on one side of the equation. If the resulting expression for y can be expressed as a single output for each input x, then y is a function of x.
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Solving Logarithmic Equations