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Ch. 1 - Equations and Inequalities
Blitzer - College Algebra 8th Edition
Blitzer8th EditionCollege AlgebraISBN: 9780136970514Not the one you use?Change textbook
Chapter 2, Problem 174

Write a quadratic equation in general form whose solution set is {- 3, 5}.

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1
Start by recalling that if the solution set of a quadratic equation is given as {x₁, x₂}, the equation can be written in factored form as (x - x₁)(x - x₂) = 0. Here, the solutions are x₁ = -3 and x₂ = 5.
Substitute the given solutions into the factored form: (x - (-3))(x - 5) = 0. Simplify the double negative to get (x + 3)(x - 5) = 0.
Expand the factored form using the distributive property: (x + 3)(x - 5) = x² - 5x + 3x - 15.
Combine like terms to simplify the expanded expression: x² - 5x + 3x - 15 = x² - 2x - 15.
Write the quadratic equation in general form: x² - 2x - 15 = 0. This is the required equation whose solution set is {-3, 5}.

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Key Concepts

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

Quadratic Equation

A quadratic equation is a polynomial equation of degree two, typically expressed in the form ax² + bx + c = 0, where a, b, and c are constants and a ≠ 0. The solutions to this equation, known as the roots, can be found using various methods such as factoring, completing the square, or the quadratic formula.
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Roots of a Quadratic

The roots of a quadratic equation are the values of x that satisfy the equation, meaning they make the equation equal to zero. For a quadratic with roots r₁ and r₂, the equation can be expressed in factored form as a(x - r₁)(x - r₂) = 0. In this case, the roots are given as -3 and 5.
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General Form of a Quadratic

The general form of a quadratic equation is written as ax² + bx + c = 0. To convert the roots into this form, one can use the factored form derived from the roots, which is a(x + 3)(x - 5). Expanding this expression will yield the general form, allowing for the identification of coefficients a, b, and c.
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