Chapter 4: Problem 55
Solve. \(6 x^{2}-23 x-55=0 \quad[3.2]\)
Short Answer
Expert verified
x = 5.5 and x = -\frac{5}{3}
Step by step solution
01
- Identify the coefficients
For the quadratic equation in the form of \(ax^2 + bx + c = 0\), identify the coefficients: \(a = 6\), \(b = -23\), and \(c = -55\).
02
- Apply the Quadratic Formula
The quadratic formula is given by \[x = \frac{-b \pm \sqrt{b^2 - 4ac}}{2a}\]. Substitute the values of \(a\), \(b\), and \(c\): \(a = 6\), \(b = -23\), and \(c = -55\).
03
- Calculate the Discriminant
Find the value under the square root (the discriminant): \(b^2 - 4ac = (-23)^2 - 4(6)(-55)\). Calculate it step-by-step: \((-23)^2 = 529\) and \(4 \times 6 \times -55 = -1320\). Put it together: \[529 - (-1320) = 529 + 1320 = 1849\].
04
- Solve for x using the Positive Root
Now calculate the two potential solutions. First, solve for the positive root: \[x = \frac{-(-23) + \sqrt{1849}}{2 \times 6} = \frac{23 + 43}{12} = \frac{66}{12} = 5.5\].
05
- Solve for x using the Negative Root
Now solve for the negative root: \[x = \frac{-(-23) - \sqrt{1849}}{2 \times 6} = \frac{23 - 43}{12} = \frac{-20}{12} = -\frac{5}{3}\].
06
- Provide the Final Solutions
The final solutions for \(x\) are: \(x = 5.5\) and \(x = -\frac{5}{3}\).
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Quadratic Formula
Understanding the quadratic formula is essential in solving quadratic equations. A quadratic equation is typically written in the form ax2 + bx + c = 0, where a, b, and c are constants. The quadratic formula helps us find the roots of the equation, which are the values of x that make the equation true. The quadratic formula is given by: \[x = \frac{-b \pm \sqrt{b^2 - 4ac}}{2a}\]This formula can be used when factoring is difficult or impossible. It's vital to remember that the formula involves a square root, which means you will need to calculate the value under the square root (the discriminant) first.
Discriminant
The discriminant is a key part of the quadratic formula and is found under the square root: \[b^2 - 4ac\]Depending on its value, the discriminant tells us the nature of the roots:
- If b2 - 4ac is positive, there are two distinct real roots.
- If it is zero, there is exactly one real root (also called a repeated or double root).
- If it is negative, there are no real roots, but two complex roots.
Roots of Quadratic Equation
Finding the roots of a quadratic equation is the final goal. Once you've used the quadratic formula and calculated the discriminant, you can solve for the roots by evaluating:\[x = \frac{-b + \sqrt{b^2 - 4ac}}{2a}\]and \[x = \frac{-b - \sqrt{b^2 - 4ac}}{2a}\]These two solutions correspond to the positive and negative roots. In the example given, we solved:
- For the positive root: \[x = \frac{23 + 43}{12} = 5.5\],
- For the negative root: \[x = \frac{23 - 43}{12} = -\frac{5}{3}\].