Chapter 3: Problem 33
Solve each equation. For equations with real solutions, support your answers graphically. $$\frac{1}{3} x^{2}-\frac{1}{3} x=24$$
Short Answer
Expert verified
The real solutions are \(x = 9\) and \(x = -8\).
Step by step solution
01
Clear Fractions
To eliminate the fractions, multiply both sides of the equation by 3. This gives:\[3 \left( \frac{1}{3} x^2 - \frac{1}{3} x \right) = 3 \times 24\]Simplifying, we have:\[x^2 - x = 72\]
02
Bring to Standard Form
Rearrange the equation to the standard quadratic form by moving all terms to one side:\[x^2 - x - 72 = 0\]
03
Factor the Quadratic Equation
To factor \(x^2 - x - 72 = 0\), we need two numbers that multiply to -72 and add to -1. These numbers are 8 and -9. Therefore, the equation can be factored as:\[(x - 9)(x + 8) = 0\]
04
Solve for x
Set each factor equal to zero to solve for \(x\):1. \(x - 9 = 0\) \implies \(x = 9\)2. \(x + 8 = 0\) \implies \(x = -8\)The solutions are \(x = 9\) and \(x = -8\).
05
Graphical Representation
The quadratic equation \(x^2 - x - 72 = 0\) is a parabola that opens upwards because the coefficient of \(x^2\) is positive. The vertex is at \(x = \frac{1}{2}\) (calculated as \(\frac{-b}{2a}\) with \(a=1, b=-1\)). The x-intercepts, which are the real solutions, are at \(x = 9\) and \(x = -8\), confirming our solutions.
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Factoring
Factoring quadratic equations is a crucial method for solving them. When we have an equation like the standard quadratic form \(x^2 - x - 72 = 0\), our task is to express it as a product of two binomials. This is based on finding two numbers that multiply to the constant term, here \(-72\), and add to the linear coefficient, here \(-1\). In factoring, you will often:
- Look for two numbers that multiply to the constant term, in this case \(-72\).
- Ensure these numbers also add up to the linear coefficient, \(-1\).
Graphical Representation
Understanding the graphical representation of a quadratic equation can enhance our grasp of its solutions. Upon conversion into standard form, our equation becomes \(x^2 - x - 72 = 0\), plotted as a parabola. This parabola opens upwards because the coefficient of \(x^2\) is positive.When graphing:
- The parabola’s shape depends on the coefficient of \(x^2\). If it's positive, it opens upward; if negative, downward.
- Identify the vertex, calculated as \(x = \frac{-b}{2a}\) for the quadratic \(ax^2 + bx + c\). Here, the vertex occurs at \(x = \frac{1}{2}\).
Solutions of Quadratics
Solving quadratic equations offers us insight into the potential values of \(x\) that satisfy the equation. When the quadratic is factored, like \((x - 9)(x + 8) = 0\), each factor is set to zero to find these solutions.This process involves:
- Setting each binomial factor equal to zero: \(x - 9 = 0\) yields \(x = 9\), and \(x + 8 = 0\) results in \(x = -8\).
- These solutions are immediately applicable because substituting them into the original equation satisfies it completely.