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Ch. 3 - Polynomial and Rational Functions
Lial - College Algebra 13th Edition
Lial13th EditionCollege AlgebraISBN: 9780136881063당신이 사용하는 게 아니라요?교과서 변경
4장, 문제 49

Several graphs of the quadratic function ƒ(x) = ax2 + bx + c are shown below. For the given restrictions on a, b, and c, select the corresponding graph from choices A–F. (Hint: Use the discriminant.) A > 0; b2 - 4ac > 0

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1
Recall the quadratic function is given by \(f(x) = ax^2 + bx + c\), where \(a\), \(b\), and \(c\) are constants.
Understand the given conditions: \(a > 0\) means the parabola opens upward, so the graph should be a 'U' shape opening upwards.
Use the discriminant formula \(\Delta = b^2 - 4ac\) to determine the nature of the roots. Since \(b^2 - 4ac > 0\), the quadratic has two distinct real roots.
Interpret these conditions graphically: the parabola opens upward and crosses the x-axis at two distinct points (because of two real roots).
From the given graphs A–F, select the one that shows a parabola opening upward and intersecting the x-axis at two distinct points.

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주요 개념

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

Quadratic Function and Its Graph

A quadratic function is a polynomial of degree two, expressed as ƒ(x) = ax² + bx + c. Its graph is a parabola that opens upward if a > 0 and downward if a < 0. The coefficients a, b, and c determine the shape and position of the parabola on the coordinate plane.
추천 영상:
5:26
Graphs of Logarithmic Functions

Discriminant of a Quadratic Equation

The discriminant, given by b² - 4ac, indicates the nature of the roots of a quadratic equation. If the discriminant is greater than zero, the equation has two distinct real roots, meaning the parabola intersects the x-axis at two points. This helps in identifying the correct graph based on root behavior.
추천 영상:
04:11
The Discriminant

Effect of Coefficient 'a' on Parabola Orientation

The coefficient 'a' in the quadratic function determines the direction the parabola opens. When a > 0, the parabola opens upward, resembling a 'U' shape. This is crucial for selecting the correct graph since the problem specifies a > 0, so the parabola must open upwards.
추천 영상:
5:28
Horizontal Parabolas