Chapter 1: Problem 67
Transform the function into the form \(f(x)=c(x-h)^{2}+k,\) where \(c, k,\) and \(h\) are constants, by completing the square. Use graph-shifting techniques to graph the function. $$f(x)=2 x^{2}-8 x+3$$
Short Answer
Expert verified
Rewrite as \( f(x) = 2(x-2)^2 - 5 \). Graph with vertex at (2, -5).
Step by step solution
01
Identify the Quadratic Terms
We start with the quadratic function given: \( f(x) = 2x^2 - 8x + 3 \). The goal is to rewrite this function in the form \( f(x) = c(x-h)^2 + k \) by completing the square.
02
Factor Out the Coefficient of x²
The term \( 2x^2 \) has a coefficient of 2. Factor 2 out of the first two terms: \[ f(x) = 2(x^2 - 4x) + 3 \]
03
Complete the Square
To complete the square, focus on the expression inside the parentheses: \( x^2 - 4x \). Take half of the linear term coefficient (-4), which is -2, and square it, resulting in 4. Add and subtract this square inside the parentheses:\[ f(x) = 2(x^2 - 4x + 4 - 4) + 3 \]This simplifies inside the parentheses to:\[ f(x) = 2((x^2 - 4x + 4) - 4) + 3 \]
04
Write as a Perfect Square and Simplify
The expression \( x^2 - 4x + 4 \) is a perfect square: \( (x-2)^2 \). Substitute this back into the equation:\[ f(x) = 2((x-2)^2 - 4) + 3 \]Distribute the 2 and simplify:\[ f(x) = 2(x-2)^2 - 8 + 3 \]\[ f(x) = 2(x-2)^2 - 5 \]
05
Identify c, h, and k
Now, the function is in the form \( f(x) = c(x-h)^2 + k \), where \( c = 2 \), \( h = 2 \), and \( k = -5 \).
06
Graph the Function
Using graph-shifting techniques based on the transformation: - \( c = 2 \): Vertical stretch by a factor of 2.- \( h = 2 \): Shift right by 2 units.- \( k = -5 \): Shift down by 5 units.Plot the vertex at \( (h, k) = (2, -5) \) and sketch the parabola opening upwards.
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.
Quadratic Function
A quadratic function is a type of function that can be written in the form \( f(x) = ax^2 + bx + c \). It's a polynomial of degree two, where the graph of this function forms a parabola. There are some key features that help in understanding quadratic functions better:
- Standard Form: The traditional representation is \( f(x) = ax^2 + bx + c \).
- Vertex: The highest or lowest point of the parabola. The location of the vertex helps in graphing the parabola accurately.
- Axis of Symmetry: A vertical line that runs through the vertex, typically given by the formula \( x = -\frac{b}{2a} \).
- Direction: If the coefficient \( a \) is positive, the parabola opens upwards. If \( a \) is negative, it opens downwards.
Vertex Form
Vertex form is an alternative way to express a quadratic function. It makes it easy to identify the vertex and thus graph the parabola efficiently. The vertex form of a quadratic function is given by:\[ f(x) = c(x - h)^2 + k \]Here's why vertex form is particularly useful:
- Immediate Identification: The values \( h \) and \( k \) represent the vertex of the parabola \( (h, k) \).
- Simplifies Graphing: Once in vertex form, graphing the function involves a simple translation of the basic parabola \( y = x^2 \).
- Graph Translation Insights: The parameter \( c \) impacts the width and direction of the parabola, while \( h \) and \( k \) indicate horizontal and vertical shifts.
Graph-shifting Techniques
Graph-shifting techniques are useful when graphing transformed equations, particularly those in vertex form. Understanding these helps visualize how a parabola's position changes on a coordinate plane.
- Horizontal Shift: The value \( h \) in the vertex form \( (x - h)^2 \) moves the graph left or right. If \( h \) is positive, shift right; if negative, shift left.
- Vertical Shift: The constant \( k \) dictates how much we move up or down. If \( k \) is positive, shift up; if negative, shift down.
- Vertical Stretch/Compression: The coefficient \( c \) affects the graph's shape. A larger \( |c| \) causes a vertical stretch, making the parabola narrower, while a smaller \( |c| \) results in a compression, making it wider.