Chapter 11: Problem 24
Solve polynomial inequality and graph the solution set on a real number line. \(x^{2} \leq 2 x+2\)
Short Answer
Expert verified
The solution of given inequality \(x^{2} \leq 2 x+2\) is \(1 - \sqrt{3} \leq x \leq 1 + \sqrt{3}\)
Step by step solution
01
Step 1
Firstly, arrange the inequality to make one side equals to zero. So, subtract \(2x + 2\) from both sides to get \(x^{2} - 2x - 2 \leq 0\)
02
Step 2
For second step, solve the equality \(x^{2} - 2x - 2 = 0\). This will provide potential points on the number line where the sign of the intervals might change. The quadratic formula is used to solve this, which is \(x = {-b \pm \sqrt{b^2-4ac}}/{2a}\). In this equation, \(a = 1\), \(b = -2\), and \(c = -2\). Plug these values into the formula to get the solutions.
03
Step 3
Using the above values, we get \(x = {2 \pm \sqrt{(-2)^2-4(1)(-2)}}/{2(1)}\). Which further simplifies to \(x = 1 \pm \sqrt{3}\). So, \(x = 1- \sqrt{3}\) and \(x = 1+ \sqrt{3}\).
04
Step 4
Since the coefficient of \(x^2\) is positive, the graph of the quadratic equation is a U shape, and we are looking for where the graph is \(\leq 0\), so the solution will be between the zeros \(1 - \sqrt{3} \leq x \leq 1 + \sqrt{3}\)
05
Step 5
The final solution of the inequality can be graphically presented as marking \(x = 1- \sqrt{3}\) and \(x = 1+ \sqrt{3}\) on the x-axis (number line), and filling in the range between these points including endpoints.
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Quadratic Formula
The quadratic formula is a powerful tool used to solve quadratic equations of the form \(ax^2 + bx + c = 0\). This formula provides the solutions or "roots" of the equation and is given by:
The term under the square root, \(b^2 - 4ac\), is called the discriminant. It determines the number and type of roots:
- \( x = \frac{-b \pm \sqrt{b^2 - 4ac}}{2a} \)
The term under the square root, \(b^2 - 4ac\), is called the discriminant. It determines the number and type of roots:
- If the discriminant is positive, there are two distinct real roots.
- If it is zero, there is exactly one real root.
- If negative, there are two complex roots.
Number Line Graphing
Number line graphing is a visual representation of the solutions of an inequality or an equation. It helps in understanding which intervals satisfy the given mathematical condition by marking critical points on a number line and analyzing intervals between them.
These steps help ensure accurate graphing of a number line:
These steps help ensure accurate graphing of a number line:
- Identify the solution points from the inequality or equation roots. Here, the roots were \(x = 1 - \sqrt{3}\) and \(x = 1 + \sqrt{3}\).
- Mark these roots as critical points on the number line with appropriate symbols, like dots or circles, indicating whether they are included or not.
- Test intervals between these critical points to determine where the inequality is true.
- Shade the section of the number line that satisfies the inequality. In this case, the solution is the interval \([1 - \sqrt{3}, 1 + \sqrt{3}]\).
Quadratic Inequality Solution
Solving a quadratic inequality involves finding the set of values for which the inequality holds. We generally follow these steps:
Start by expressing the inequality such that one side is zero. For \(x^2 \leq 2x + 2\), rearrange to \(x^2 - 2x - 2 \leq 0\).
Start by expressing the inequality such that one side is zero. For \(x^2 \leq 2x + 2\), rearrange to \(x^2 - 2x - 2 \leq 0\).
- Use the quadratic formula to solve the equivalent equation \(x^2 - 2x - 2 = 0\) to find where the expression may change signs.
- These solutions \(x = 1 \pm \sqrt{3}\) act as boundaries on the number line.
- Determine the nature of intervals around these points by testing them. Since the parabola opens upwards (U-shape) and includes \(\leq 0\), the area shaded between and including the two roots represents the solution.
- The final solution, \([1 - \sqrt{3}, 1 + \sqrt{3}]\), is indicated on the number line with solid dots, showing that both boundary values are part of the solution set.