X 2 6x 7 0

Introduction

The quadratic equation x² + 6x + 7 = 0 is a classic example of a second-degree polynomial equation that appears frequently in algebra, physics, and engineering. Solving this equation involves finding the values of x that make the equation true. Quadratic equations like this one are fundamental in mathematics because they model many real-world phenomena, from projectile motion to optimization problems. In this article, we will explore how to solve this equation, understand its properties, and see why it matters in both academic and practical contexts.

Detailed Explanation

A quadratic equation is any equation that can be written in the standard form ax² + bx + c = 0, where a, b, and c are constants and a ≠ 0. In the equation x² + 6x + 7 = 0, the coefficients are a = 1, b = 6, and c = 7. The goal is to find the roots or solutions for x, which are the values that satisfy the equation. These solutions can be real or complex numbers, depending on the discriminant (b² - 4ac). Quadratic equations are essential in algebra because they introduce students to more complex problem-solving techniques beyond linear equations.

The quadratic formula, x = [-b ± √(b² - 4ac)] / (2a), is the most reliable method for solving any quadratic equation. For x² + 6x + 7 = 0, plugging in the values gives us x = [-6 ± √(36 - 28)] / 2, which simplifies to x = [-6 ± √8] / 2. This further simplifies to x = -3 ± √2. Therefore, the solutions are x = -3 + √2 and x = -3 - √2. These are irrational numbers, meaning they cannot be expressed as simple fractions, but they are exact solutions to the equation.

Step-by-Step or Concept Breakdown

To solve x² + 6x + 7 = 0, follow these steps:

1. Identify the coefficients: a = 1, b = 6, c = 7.
2. Calculate the discriminant: b² - 4ac = 36 - 28 = 8.
3. Apply the quadratic formula: x = [-6 ± √8] / 2.
4. Simplify the square root: √8 = 2√2, so x = [-6 ± 2√2] / 2.
5. Reduce the fraction: x = -3 ± √2.

The discriminant being positive (8 > 0) tells us there are two distinct real roots. If the discriminant were zero, there would be one repeated real root, and if it were negative, the roots would be complex. In this case, the roots are irrational but real, which is common for many quadratic equations.

Real Examples

Quadratic equations like x² + 6x + 7 = 0 appear in many real-world scenarios. For example, in physics, the trajectory of a projectile can be modeled by a quadratic equation. If a ball is thrown upward, its height over time can be described by an equation of the form h(t) = -16t² + vt + h₀, where v is the initial velocity and h₀ is the initial height. Solving such equations helps determine when the ball will hit the ground.

In economics, quadratic equations can model profit functions. If a company's profit is given by P(x) = -2x² + 100x - 800, solving P(x) = 0 helps find the break-even points where profit is zero. Similarly, in engineering, quadratic equations describe the shape of parabolic structures like satellite dishes or suspension bridges.

Scientific or Theoretical Perspective

From a theoretical standpoint, the quadratic formula is derived by completing the square on the general quadratic equation. This method transforms the equation into a perfect square trinomial, making it easier to solve. The discriminant, b² - 4ac, is a key part of this theory because it determines the nature of the roots without actually solving the equation. A positive discriminant indicates two distinct real roots, zero indicates one repeated real root, and a negative discriminant indicates two complex conjugate roots.

The roots of x² + 6x + 7 = 0 are -3 + √2 and -3 - √2. These can be verified by substituting them back into the original equation. For example, plugging in x = -3 + √2 gives (-3 + √2)² + 6(-3 + √2) + 7 = 0, which simplifies correctly. This verification process is important in mathematics to ensure the solutions are accurate.

Common Mistakes or Misunderstandings

One common mistake when solving quadratic equations is forgetting to simplify the square root in the quadratic formula. In this case, √8 should be simplified to 2√2 before dividing by 2. Another error is misidentifying the coefficients, especially the sign of b. If the equation were x² - 6x + 7 = 0, the solutions would be different.

Students sometimes also confuse the discriminant with the roots themselves. The discriminant only tells us the nature of the roots, not their exact values. Additionally, some may try to factor the equation directly, but x² + 6x + 7 does not factor nicely over the integers, which is why the quadratic formula is necessary here.

FAQs

Q: Can x² + 6x + 7 = 0 be factored? A: No, this quadratic does not factor nicely over the integers. The roots are irrational, so factoring would require irrational numbers.

Q: What does the discriminant tell us about this equation? A: The discriminant is 8, which is positive, indicating two distinct real roots.

Q: Are the roots of this equation rational or irrational? A: The roots are irrational because √2 is an irrational number.

Q: How can I check if my solutions are correct? A: Substitute the roots back into the original equation. If both sides equal zero, the solutions are correct.

Conclusion

The quadratic equation x² + 6x + 7 = 0 is a perfect example of how algebra connects to both theory and real-world applications. By using the quadratic formula, we find the solutions to be x = -3 + √2 and x = -3 - √2. Understanding how to solve such equations is crucial for students and professionals alike, as quadratics appear in physics, engineering, economics, and many other fields. Mastering these concepts builds a strong foundation for more advanced mathematics and problem-solving skills.