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Solve using any method. $$8 w^{2}+2 w-21=0$$

Short Answer

Expert verified
The solutions are \(w = \frac{3}{2}\) and \(w = -\frac{7}{4}\).

Step by step solution

01

Identify the Standard Form

The given equation is already in standard quadratic form: \(8w^2 + 2w - 21 = 0\). Here, \(a = 8\), \(b = 2\), and \(c = -21\). The standard quadratic equation is \(ax^2 + bx + c = 0\).
02

Use the Quadratic Formula

The quadratic formula is given by: \[w = \frac{-b \pm \sqrt{b^2 - 4ac}}{2a}\]Substitute \(a = 8\), \(b = 2\), and \(c = -21\) into the formula.
03

Calculate the Discriminant

The discriminant \(D\) is calculated as \(b^2 - 4ac\).Substitute the values: \(D = 2^2 - 4 \cdot 8 \cdot (-21)\).Calculate \(D = 4 + 672 = 676\). Since 676 is a perfect square, it indicates that the solutions are real and rational.
04

Solve for the Roots

Replace \(D\) in the quadratic formula to find the roots:\[w = \frac{-2 \pm \sqrt{676}}{16}\].\(\sqrt{676} = 26\). So:\[w = \frac{-2 + 26}{16}\] and \[w = \frac{-2 - 26}{16}\].
05

Simplify the Solutions

Compute the two values:\[w = \frac{24}{16} = \frac{3}{2}\]\[w = \frac{-28}{16} = -\frac{7}{4}\]Thus, the solutions for \(w\) are \(w = \frac{3}{2}\) and \(w = -\frac{7}{4}\).

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Key Concepts

These are the key concepts you need to understand to accurately answer the question.

Quadratic Formula
In the world of algebra, solving quadratic equations is a frequent task, and one powerful tool for the job is the quadratic formula. This formula is especially handy when factorizing the equation is difficult or impossible. To use the quadratic formula, ensure your equation is in standard form: \(ax^2 + bx + c = 0\). Here, \(a\), \(b\), and \(c\) represent coefficients, and they can help you find the value of \(x\). When you're ready to apply it, the formula is:
  • \[x = \frac{-b \pm \sqrt{b^2 - 4ac}}{2a}\]
The output provides two solutions due to the '±' symbol, which accounts for both the addition and subtraction of the square root term. Always plug in the respective values for the coefficients into the formula. This universal solution makes the quadratic formula a cornerstone in mathematical problem-solving.
Discriminant
In any quadratic equation, the discriminant plays a crucial role in discerning the nature of the equation's solutions. It's calculated using the expression \(b^2 - 4ac\). Depending on the value of the discriminant, you can determine how many and what type of solutions you should expect. Here's a breakdown:
  • If \(D > 0\), the quadratic equation has two distinct real solutions.
  • If \(D = 0\), it has exactly one real solution, also known as a repeated or double root.
  • If \(D < 0\), the solutions are complex or imaginary, not real.
The discriminant helps in making predictions even before solving, saving time and guiding your approach. In the solved exercise, the discriminant was 676, and since it is a perfect square, it prompted real and rational solutions. This hints that understanding the discriminant not only adds clarity but also speeds up the problem-solving process.
Real and Rational Solutions
After calculating the discriminant and concluding that it offers real and rational solutions, we can expect straightforward, clean solutions. Real solutions are numbers that you can point to on a number line, while rational solutions can be expressed as a fraction of two integers. In the exercise's context:
  • The roots solved using the quadratic formula were \(w = \frac{3}{2}\) and \(w = -\frac{7}{4}\).
  • Both numbers are rational since they can be written as exact fractions.
  • The fact that they stem from a perfect square discriminant confirms their rational nature.
Rational solutions are often easier to interpret and use in further calculations. Having these on hand simplifies both analysis and application in real-world contexts. Remember this attribute to quickly identify the nature of your solutions when you're tackling similar quadratic problems.

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