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Ch. 3 - Polynomial and Rational Functions
Blitzer - College Algebra 8th Edition
Blitzer8th EditionCollege AlgebraISBN: 9780136970514Not the one you use?Change textbook
All textbooksBlitzer 8th EditionCh. 3 - Polynomial and Rational FunctionsProblem 27
Chapter 4, Problem 27

Use the vertex and intercepts to sketch the graph of each quadratic function. Give the equation of the parabola's axis of symmetry. Use the graph to determine the function's domain and range. f(x)=x2−2x−3

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1
Identify the quadratic function given: \(f(x) = x^{2} - 2x - 3\).
Find the vertex of the parabola using the formula for the x-coordinate of the vertex: \(x = -\frac{b}{2a}\). Here, \(a = 1\) and \(b = -2\), so calculate \(x = -\frac{-2}{2 \times 1}\).
Substitute the x-coordinate of the vertex back into the function to find the y-coordinate: \(f\left(-\frac{b}{2a}\right) = \left(-\frac{b}{2a}\right)^{2} - 2\left(-\frac{b}{2a}\right) - 3\).
Find the y-intercept by evaluating \(f(0)\), which is simply the constant term in this case, and find the x-intercepts by solving the quadratic equation \(x^{2} - 2x - 3 = 0\) using factoring or the quadratic formula.
Write the equation of the axis of symmetry as \(x = -\frac{b}{2a}\), determine the domain (all real numbers), and use the vertex and direction of the parabola (since \(a > 0\), it opens upward) to describe the range.

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Key Concepts

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

Vertex of a Quadratic Function

The vertex is the highest or lowest point on the parabola, representing its maximum or minimum value. It can be found using the formula x = -b/(2a) for a quadratic function in standard form f(x) = ax² + bx + c. The vertex helps in sketching the graph and understanding the parabola's shape.
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Vertex Form

Axis of Symmetry

The axis of symmetry is a vertical line that passes through the vertex, dividing the parabola into two mirror-image halves. Its equation is x = -b/(2a). This line is crucial for graphing because it shows the parabola's symmetry and helps locate points on either side.
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Properties of Parabolas

Domain and Range of Quadratic Functions

The domain of any quadratic function is all real numbers since x can take any value. The range depends on the vertex: if the parabola opens upward (a > 0), the range is all y-values greater than or equal to the vertex's y-coordinate; if it opens downward (a < 0), the range is all y-values less than or equal to the vertex's y-coordinate.
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Domain & Range of Transformed Functions
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