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Ch. 5 - Systems of Equations and Inequalities
Blitzer - College Algebra 8th Edition
Blitzer8th EditionCollege AlgebraISBN: 9780136970514Not the one you use?Change textbook
Chapter 6, Problem 21

Find the quadratic function y = ax2+bx+c whose graph passes through the given points. (−1,−4), (1,−2), (2, 5)

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Identify the general form of the quadratic function: \(y = ax^{2} + bx + c\), where \(a\), \(b\), and \(c\) are constants to be determined.
Substitute each given point into the quadratic equation to create a system of equations. For the point \((-1, -4)\), substitute \(x = -1\) and \(y = -4\) to get: \(a(-1)^{2} + b(-1) + c = -4\).
Similarly, substitute the point \((1, -2)\) into the equation: \(a(1)^{2} + b(1) + c = -2\).
Substitute the point \((2, 5)\) into the equation: \(a(2)^{2} + b(2) + c = 5\).
Solve the resulting system of three equations with three unknowns (\(a\), \(b\), and \(c\)) using methods such as substitution, elimination, or matrix operations to find the values of \(a\), \(b\), and \(c\).

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Key Concepts

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

Quadratic Functions

A quadratic function is a polynomial of degree two, generally written as y = ax² + bx + c, where a, b, and c are constants and a ≠ 0. Its graph is a parabola that opens upward if a > 0 and downward if a < 0.
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System of Equations

To find the coefficients a, b, and c of the quadratic function, you substitute the given points into the equation y = ax² + bx + c, creating a system of linear equations. Solving this system yields the values of a, b, and c.
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Substitution and Solving Linear Systems

Substitution involves replacing variables with known values to form equations. Solving the resulting system of linear equations can be done using methods like substitution, elimination, or matrix operations to find the unknown coefficients.
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