Chapter 11: Problem 13
\(3-16=\) Graph the inequality. $$ y>x^{2}+1 $$
Short Answer
Expert verified
Graph the parabola \(y = x^2 + 1\) as a dashed line and shade above it.
Step by step solution
01
Understand the Inequality
The inequality we are dealing with is \( y > x^2 + 1 \). This is a quadratic inequality where the right side is a quadratic expression \( x^2 + 1 \). Our goal is to graph the region where the value of \( y \) is greater than the value of this quadratic expression.
02
Graph the Parabola
Graph the parabola \( y = x^2 + 1 \). This serves as the boundary for our inequality. The graph of \( y = x^2 + 1 \) is a standard upward-opening parabola that is shifted one unit upwards along the y-axis.
03
Determine the Boundary Type
Since the inequality is \( y > x^2 + 1 \) (and not \( y \geq x^2 + 1 \)), the boundary line (parabola) \( y = x^2 + 1 \) is dashed. This indicates that points on the parabola are not included in the solution set.
04
Shade the Correct Region
Shade the region above the parabola \( y = x^2 + 1 \). This is where \( y \) is greater than \( x^2 + 1 \). You can test a point above the parabola (like (0, 2)) to confirm that the inequality holds, ensuring you're shading the correct area.
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Quadratic Inequalities
A quadratic inequality involves an algebraic expression with a quadratic term, which is an expression that includes a squared variable, such as \( x^2 \). In our example, the inequality given is \( y > x^2 + 1 \). Here, the goal is to find the solution set of \( y \) values that are greater than \( x^2 + 1 \). Understanding this is crucial, as it's not just about solving for x or y -- it’s about determining the range of solutions that satisfy the inequality within a graphing context.
- A quadratic inequality can take forms like \( y < x^2 + bx + c \) or \( y > x^2 + bx + c \).
- These inequalities define regions on the coordinate plane to graphically solve them.
- The solution is often a region, not a specific set of values.
Parabola Graphing
Graphing a parabola is an essential step when dealing with quadratic inequalities. A parabola is a symmetrical curve represented by a quadratic equation such as \( y = x^2 + 1 \). To graph it, you follow these steps:
- Identify the vertex: For \( y = x^2 + 1 \), the vertex is \( (0, 1) \), since it’s given by the lowest point on the curve when it opens upward.
- Determine the direction: An upward opening happens because the coefficient of \( x^2 \) is positive.
- Draw the axis of symmetry: A vertical line through the vertex at \( x = 0 \).
- Sketch the parabola: Start at the vertex (0,1) and plot additional points to form a curve.
Inequality Region Shading
Shading the correct region is vital for showing the solutions to a quadratic inequality on a graph. In the case of \( y > x^2 + 1 \), you need to shade the region above the parabola because any point in this area satisfies the inequality.
- The inequality sign \( > \) directs you to shade above the parabola.
- Use a dashed boundary to indicate that points on the line are not part of the solution set.
- Pick a test point such as (0, 2). Substitute into the inequality: \( 2 > 0^2 + 1 \), which simplifies to \( 2 > 1 \). This holds true, confirming the correct region is above the parabola.