Chapter 8: Problem 22
Systems of Equations and Inequalities. $$y \geq x^{2}-1$$
Short Answer
Expert verified
The solution to the inequality \(y \geq x^{2}-1\) is all the points (x, y) that lie above and on the curve of the parabola \(y = x^{2}-1\).
Step by step solution
01
Understand the inequality
The inequality \(y \geq x^{2} - 1\) is expressed in terms of \(y\) and \(x\). \(x^{2} - 1\) represents a parabola, which opens upwards. Here, the value of 'y' is greater than or equal to 'x' squared minus one.
02
Graph the inequality
To graph \(y \geq x^{2}-1\), first, plot the parabola of \(y = x^{2}-1\). The vertex of this parabola is at the origin, and the parabola will open upwards. As the inequality is \(y \geq\), the area above the curve \(y = x^{2}-1\), including the curve, represents the solution to the inequality.
03
Define the solution
The solution of the inequality \(y \geq x^{2}-1\) is the region that lies above the parabola \(y = x^{2}-1\), including the curve. In other words, each point in that region makes the inequality true. Therefore, any point (x, y) that lies in this region is a solution to the inequality.
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Graphing Inequalities
Graphing inequalities involves plotting a region on a coordinate plane that satisfies the inequality. In our exercise, the inequality is \( y \geq x^2 - 1 \). This inequality indicates that we need to graph all points where the value of \( y \) is either equal to or greater than \( x^2 - 1 \).
- **Step 1: Plot the boundary**. First, we identify the curve \( y = x^2 - 1 \). This is the boundary line of our inequality, which forms a parabola. It's essential to draw this line precisely since it shows where \( y \) equals exactly \( x^2 - 1 \).
- **Step 2: Determine the shading**. Since \( y \geq x^2 - 1 \), the area above the parabola is shaded. This shading includes the region and the boundary line itself because the inequality includes \( \geq \) (greater than or equal to).
- **Step 3: Use test points**. If you're unsure about the shading direction, pick a test point not on the boundary line (like the origin, \( (0,0) \)), and substitute it into the inequality to see if it holds true. This is a useful technique to confirm your shaded area.
Parabolas
A parabola is a U-shaped curve that can open either upwards or downwards. It is defined by a quadratic equation, such as \( y = x^2 - 1 \) in our example. Understanding the properties of parabolas is key to graphing them accurately.
- **Vertex**: The vertex is the tip of the parabola. For \( y = x^2 - 1 \), the vertex is at \( (0, -1) \). It is a crucial point as it acts as the parabola's lowest point (for upward opening) or highest point (for downward opening).
- **Direction**: The expression \( y = x^2 - 1 \) indicates an upward opening parabola because the \( x^2 \) term is positive. If the term was negative, the parabola would open downwards.
- **Axis of Symmetry**: Parabolas have an axis of symmetry, a vertical line that passes through the vertex. For our parabola, this line is \( x = 0 \), which runs vertically through the vertex.
Solution of Inequalities
When solving inequalities, the objective is to identify all possible values that will make the inequality true. With \( y \geq x^2 - 1 \), we're interested in finding all pairs \( (x, y) \) that satisfy this condition.
- **Identify the boundary**: First, determine the equality \( y = x^2 - 1 \). This equation helps to visualize the limit of the solutions. The boundary itself is included in the solutions because of the "equal to" part of \( \geq \).
- **Understanding the region**: The inequality encompasses all **above** or **on** the parabola \( y = x^2 - 1 \). Any point in this region will satisfy the inequality.
- **Multiple solutions**: Unlike equations with one or two solutions (like linear or quadratic equations), inequalities often have infinite solutions. These solutions form a region instead of discrete points.