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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 65

Solve each equation in Exercises 65–74 using the quadratic formula. x2+8x+15=0x^2 + 8x + 15 = 0

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Identify the coefficients in the quadratic equation \(x^2 + 8x + 15 = 0\). Here, \(a = 1\), \(b = 8\), and \(c = 15\).
Recall the quadratic formula: \(x = \frac{-b \pm \sqrt{b^2 - 4ac}}{2a}\).
Substitute the values of \(a\), \(b\), and \(c\) into the quadratic formula: \(x = \frac{-8 \pm \sqrt{8^2 - 4 \cdot 1 \cdot 15}}{2 \cdot 1}\).
Simplify inside the square root (the discriminant): calculate \(8^2 - 4 \cdot 1 \cdot 15\) to determine the value under the square root.
Evaluate the square root and then compute the two possible values for \(x\) by using the plus and minus signs in the formula.

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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 second-degree polynomial equation in the form ax² + bx + c = 0, where a ≠ 0. It represents a parabola when graphed, and its solutions are the x-values where the parabola intersects the x-axis.
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Quadratic Formula

The quadratic formula x = (-b ± √(b² - 4ac)) / (2a) provides the solutions to any quadratic equation ax² + bx + c = 0. It uses coefficients a, b, and c to find roots, including real and complex solutions.
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Discriminant

The discriminant, given by b² - 4ac, determines the nature of the roots of a quadratic equation. If positive, there are two distinct real roots; if zero, one real root; and if negative, two complex conjugate roots.
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