Chapter 3: Problem 25
Solve each equation. For equations with real solutions, support your answers graphically. $$x^{2}=2 x+24$$
Short Answer
Expert verified
The real solutions are \(x = 6\) and \(x = -4\).
Step by step solution
01
Move all terms to one side
Start by rewriting the given equation: \[ x^2 = 2x + 24 \]Subtract \(2x\) and \(24\) from both sides to set the equation to zero:\[ x^2 - 2x - 24 = 0 \]
02
Factor the quadratic equation
Look for two numbers that multiply to \(-24\) and add to \(-2\). These numbers are \(-6\) and \(4\). Write the equation as:\[ (x - 6)(x + 4) = 0 \]
03
Solve for x
Set each factor equal to zero and solve for \(x\):\[ x - 6 = 0 \Rightarrow x = 6 \]\[ x + 4 = 0 \Rightarrow x = -4 \]The solutions are \(x = 6\) and \(x = -4\).
04
Verify solutions graphically
Graph the equation \(y = x^2 - 2x - 24\). The solutions are the x-intercepts of the graph, which occur where \(y = 0\). Verify that the x-intercepts are at \(x = 6\) and \(x = -4\).
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Factoring Quadratics
Factoring quadratics is a powerful technique to solve quadratic equations in the form of \(ax^2+bx+c=0\). The goal is to express the quadratic equation as a product of linear factors.For instance, in the original exercise, we had the equation \(x^2 - 2x - 24 = 0\). To factor it, you find two numbers that multiply to \(-24\) (the constant term) and add to \(-2\) (the coefficient of the linear term). After thinking through possible pairs, you find that \(-6\) and \(4\) work. This way, the quadratic expression becomes \((x - 6)(x + 4) = 0\). The beauty of factoring is:
- It converts the quadratic equation into simpler linear equations.
- It gives you the solutions directly when each factor is set to zero.
Graphical Solution
In solving quadratic equations, the graphical solution offers a visual understanding of the equation's roots. By graphing the equation \(y = x^2 - 2x - 24\), you look for points where the graph intersects the x-axis. These intersection points are the solutions to the original equation, also known as the x-intercepts. Graphically, this process helps:
- Confirm the solutions calculated algebraically.
- Understand the nature of solutions. If you see two x-intercepts, there are real solutions. No x-intercepts mean no real solutions.
- Visualize how changes in the equation affect the graph and the roots.
Quadratic Formula
The quadratic formula is a universal tool to find solutions of any quadratic equation, regardless of whether it can be factored easily or not.Given any quadratic equation in the form \(ax^2 + bx + c = 0\), the solutions can be found using the formula:\[ x = \frac{{-b \pm \sqrt{{b^2 - 4ac}}}}{2a} \]This formula always works and provides solutions even when:
- The equation cannot be factored directly or easily.
- There are complex or irrational roots involved.
X-intercepts
X-intercepts are crucial in understanding the behavior of quadratic graphs in relation to their equations. They represent the values of \(x\) where the graph hits or crosses the x-axis, meaning \(y=0\) at these points. In our solved equation, the solutions were \(x=6\) and \(x=-4\), which are precisely the x-intercepts of the graph of \(y=x^2-2x-24\).These intercepts are essential because:
- They reveal the real solutions to the quadratic equation.
- They show where a projectile, in applications, would land on a horizontal surface.
- They help in determining the range and roots visually on a graph.