Chapter 9: Problem 4
Graph each of the following linear and quadratic functions. $$f(x)=-4 x^{2}$$
Short Answer
Expert verified
The function is a downward-opening parabola with the vertex at (0,0).
Step by step solution
01
Identify the Function Type
The given function is \(f(x) = -4x^2\). This is a quadratic function, as it is in the form of \(ax^2 + bx + c\). Here, \(a = -4\), \(b = 0\), and \(c = 0\). Quadratic functions graph to form a parabola.
02
Determine the Vertex
For the function \(f(x) = ax^2\), the vertex is at \((0, 0)\) if it is in the form \(-4x^2\) without a linear term or constant. The vertex of the parabola for this function is at the origin, \((0, 0)\).
03
Determine the Direction of the Parabola
The coefficient \(a = -4\) is negative, which means the parabola opens downwards. If \(a\) is positive, the parabola opens upwards, and if it's negative, it opens downwards.
04
Find Additional Points
Choose some x-values to substitute into the function to find corresponding y-values. For example:- If \(x = 1\), then \(f(1) = -4(1)^2 = -4\).- If \(x = -1\), then \(f(-1) = -4(-1)^2 = -4\).- If \(x = 2\), then \(f(2) = -4(2)^2 = -16\).- If \(x = -2\), then \(f(-2) = -4(-2)^2 = -16\).The points \((1, -4)\), \((-1, -4)\), \((2, -16)\), and \((-2, -16)\) can be plotted.
05
Sketch the Graph
Plot the vertex \((0, 0)\) and the additional points \((1, -4)\), \((-1, -4)\), \((2, -16)\), and \((-2, -16)\) on a coordinate grid. Draw a smooth curve connecting these points to form the parabola. Make sure the parabola opens downward.
Unlock Step-by-Step Solutions & Ace Your Exams!
-
Full Textbook Solutions
Get detailed explanations and key concepts
-
Unlimited Al creation
Al flashcards, explanations, exams and more...
-
Ads-free access
To over 500 millions flashcards
-
Money-back guarantee
We refund you if you fail your exam.
Over 30 million students worldwide already upgrade their learning with 91Ó°ÊÓ!
Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Understanding Quadratic Functions
A quadratic function is a special type of polynomial function. It has the form \(f(x) = ax^2 + bx + c\), where \(a\), \(b\), and \(c\) are constants, and \(a eq 0\). This form is known as the standard form of a quadratic function.
- **Coefficient \(a\):** This determines the direction the parabola opens. A positive \(a\) results in a parabola that opens upwards, and a negative \(a\) results in a parabola that opens downwards.
- **Terms \(b\) and \(c\):** These will affect the position of the vertex and the shape of the parabola but won’t change its general direction.
Exploring the Parabola
A parabola is the graph of a quadratic function, and it possesses a distinctive "U" shape. Specific properties make parabolas interesting and useful.
### Key Features of Parabolas
### Key Features of Parabolas
- **Direction of Opening:** The coefficient \(a\) in the quadratic function \(ax^2 + bx + c\) determines if the parabola opens upwards or downwards.
- **Symmetry:** Every parabola has an axis of symmetry, which is a vertical line that passes through the vertex. For the function \(f(x) = ax^2\), it is the y-axis itself.
- **Width:** The absolute value of \(a\) also influences the width of the parabola. A larger absolute value makes the parabola narrower, while a smaller absolute value makes it wider.
Locating the Vertex and Its Role
The vertex of a parabola is a crucial point on its graph. It represents the highest or lowest point depending on the direction the parabola opens. For the quadratic \(f(x) = ax^2 + bx + c\), finding the vertex requires some understanding of its formula.
### Determining the VertexFor a parabola described by \(f(x) = ax^2\) like in our example \(f(x) = -4x^2\), the vertex is straightforward to find:
### Determining the VertexFor a parabola described by \(f(x) = ax^2\) like in our example \(f(x) = -4x^2\), the vertex is straightforward to find:
- If the quadratic function does not include linear or constant terms (i.e., \(b = 0\) and \(c = 0\)), the vertex is at the origin \((0, 0)\).