Chapter 3: Problem 51
Use transformations to sketch a graph of \(f\). \(f(x)=-x^{2}+4\)
Short Answer
Expert verified
Reflect the base parabola downwards and shift it up by 4 units.
Step by step solution
01
Identify the Base Function
The base function is the quadratic function \(g(x) = x^2\). This is a standard parabola opening upwards and centered at the origin.
02
Reflect Across the X-axis
The function \(f(x) = -x^2 \) involves a reflection of the base function across the x-axis. This transforms the parabola to open downwards while maintaining the vertex at the origin.
03
Vertical Shift Upwards
The term \(+4\) in the function \(f(x) = -x^2 + 4\) indicates a vertical shift upwards by 4 units. This moves the vertex of the parabola from the origin to the point (0, 4).
04
Sketch the Graph
Begin with a downward-opening parabola whose vertex is at (0, 4). Plot a few points, such as (1, 3) and (-1, 3), to help guide the shape of the parabola and ensure symmetry about the vertex.
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Quadratic Function
A quadratic function is an essential concept in algebra that is commonly expressed in the form \(g(x) = ax^2 + bx + c\). The graph of a quadratic function is a parabola, which is a U-shaped curve. Three key features of a quadratic function are:
- The coefficient \(a\): If \(a > 0\), the parabola opens upwards; if \(a < 0\), it opens downwards.
- The axis of symmetry: This is a vertical line passing through the vertex of the parabola, given by \(x = -\frac{b}{2a}\).
- The vertex: This is the highest or lowest point on the graph of the parabola, located at \((-\frac{b}{2a}, f(-\frac{b}{2a}))\).
Reflection Transformation
Reflection transformation is a type of graph transformation in which a function is flipped over a line, such as the x-axis or y-axis, producing a mirror image of the original graph.
- Reflection across the X-axis: This transforms the graph of \(y = f(x)\) into \(y = -f(x)\). The reflection reverses the direction in which the parabola opens, converting upward-opening functions to downward-opening, and vice-versa.
- Reflection across the Y-axis: For even functions \(y = f(x)\), this transformation doesn't change the graph since it remains symmetric about the y-axis.
Vertical Shift
A vertical shift is a simple graph transformation that involves moving the entire graph of a function up or down in the Cartesian plane without changing its shape.
- Upward Shift: Adding a constant \(k\) to a function \(y = f(x)\) results in \(y = f(x) + k\), shifting the graph upwards by \(k\) units.
- Downward Shift: Subtracting a constant \(k\) from a function \(y = f(x)\) creates \(y = f(x) - k\), shifting the graph downwards by \(k\) units.