Chapter 1: Problem 366
For the following exercises, describe how the formula is a transformation of a toolkit function. Then sketch a graph of the transformation. $$ g(x)=4(x+1)^{2}-5 $$
Short Answer
Expert verified
\( g(x) = 4(x+1)^2 - 5 \) is a transformed \( x^2 \) with shifts and a stretch. The vertex is at \((-1, -5)\), and the parabola is narrower.
Step by step solution
01
Identify the Toolkit Function
The given function is a transformation of the toolkit function \( f(x) = x^2 \), which is the basic quadratic function.
02
Determine the Horizontal Translation
The function is \( g(x) = 4(x+1)^2 - 5 \). Notice the \((x+1)\) in the expression. This indicates a horizontal shift of the graph left by 1 unit.
03
Determine the Vertical Translation
The constant term outside the squared expression is \(-5\). This results in a vertical shift of the graph down by 5 units.
04
Determine the Vertical Stretch
The coefficient in front of the squared term is 4. This means the graph will be vertically stretched by a factor of 4. The "4" makes the parabola narrower compared to the original \( f(x) = x^2 \).
05
Combine the Transformations
Combine all three transformations: shift the graph of \( f(x) = x^2 \) left by 1 unit, down by 5 units, and apply a vertical stretch by a factor of 4. The graph of \( g(x) = 4(x+1)^2 - 5 \) is a narrow parabola that opens upwards with its vertex at \(( -1, -5 )\).
06
Sketch the Graph
Draw the new graph based on the transformations identified. The vertex will move from \((0, 0)\) to \((-1, -5)\) due to the transformations. The graph is narrower due to the stretch.
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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 one of the simplest types of polynomial functions. It takes the form \( f(x) = ax^2 + bx + c \), where \( a \), \( b \), and \( c \) are constants, and \( a eq 0 \). The graph of a quadratic function is a parabola.
- If \( a > 0 \), the parabola opens upwards.
- If \( a < 0 \), the parabola opens downwards.
Horizontal Translation
Horizontal translation refers to moving the graph of a function left or right along the x-axis. It is accomplished by adding or subtracting a constant from the variable \( x \) inside the function.
In the function \( g(x) = 4(x+1)^2 - 5 \), we observe a horizontal translation. The replacement of \( x \) with \( (x+1) \) indicates that the function is shifted to the left by 1 unit.
In the function \( g(x) = 4(x+1)^2 - 5 \), we observe a horizontal translation. The replacement of \( x \) with \( (x+1) \) indicates that the function is shifted to the left by 1 unit.
- Adding a positive number: \( (x - h) \), moves the graph to the right by \( h \) units.
- Adding a negative number: \( (x + h) \), moves the graph to the left by \( h \) units.
Vertical Translation
Vertical translation involves shifting the graph of a function up or down along the y-axis. This is achieved by adding or subtracting a constant outside the function. In our function \( g(x) = 4(x+1)^2 - 5 \), the \(-5\) at the end signifies a downward shift.
- Adding a constant: \( +k \), raises the graph by \( k \) units.
- Subtracting a constant: \( -k \), lowers the graph by \( k \) units.
Vertical Stretch
Vertical stretch is a type of transformation that alters the "height" or "width" of a graph, making it taller and narrower, or shorter and wider. It is governed by the coefficient of the squared term in a quadratic function.
For \( g(x) = 4(x+1)^2 - 5 \), the factor "4" in front of \((x+1)^2\) is responsible for the vertical stretch. This means every point on the basic parabola \( f(x) = x^2 \) is moved 4 times further from the x-axis.
For \( g(x) = 4(x+1)^2 - 5 \), the factor "4" in front of \((x+1)^2\) is responsible for the vertical stretch. This means every point on the basic parabola \( f(x) = x^2 \) is moved 4 times further from the x-axis.
- If the coefficient is greater than 1, the parabola becomes narrower.
- If the coefficient is between 0 and 1, the parabola becomes wider.
- A negative coefficient would flip the parabola upside down (not the case here as the coefficient is positive).