Chapter 9: Problem 332
(a) rewrite each function in \(f(x)=a(x-h)^{2}+k\) form and (b) graph it by using transformations. $$f(x)=x^{2}-6 x+8$$
Short Answer
Expert verified
Rewritten function: \[f(x) = (x-3)^2 - 1\].Graph using transformations: Shift right by 3 units and down by 1 unit.
Step by step solution
01
Identify the Quadratic Expression
The given function is: \[f(x) = x^2 - 6x + 8\]Recognize that this is in the standard quadratic form.
02
Rewrite as a Perfect Square Trinomial
To rewrite the quadratic function in the form \[f(x) = a(x-h)^2 + k\]complete the square.Start with the expression inside the function: \[x^2 - 6x + 8\]Take the coefficient of x (which is -6), divide it by 2, and square the result: \[\frac{-6}{2} = -3\] \[(-3)^2 = 9\]Now rewrite the quadratic expression by adding and subtracting this square term: \[x^2 - 6x + 9 - 9 + 8\]}
03
Simplify the Expression
Group the perfect square trinomial and simplify the constants: \[(x^2 - 6x + 9) - 9 + 8\]This can be written as: \[(x - 3)^2 - 1\]Thus, rewritten in vertex form: \[f(x) = (x-3)^2 - 1\]}
04
Identify Transformations
Compare the vertex form \[f(x) = (x-3)^2 - 1\] with \[f(x) = a(x-h)^2 + k\].The vertex is at \[(h, k) = (3, -1)\].This tells you the transformations relative to \[f(x) = x^2\]:- Shift right by 3 units.- Shift down by 1 unit.
05
Graph the Function
Start with the graph of \[y = x^2\].Apply the transformations:1. Shift the graph right by 3 units, so the vertex moves from \[(0, 0)\] to \[(3, 0)\].2. Shift the graph down by 1 unit, so the vertex moves from \[(3, 0)\] to \[(3, -1)\].The final graph is a parabola opening upwards with vertex at \[(3, -1)\].
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
quadratic functions
Quadratic functions are fundamental in algebra and pre-calculus. They are represented by polynomial equations of the form: y = ax^2 + bx + c.Here, 'a', 'b', and 'c' are constants, and the highest power of the variable x is 2, making it a second-degree polynomial. The graph of a quadratic function is a parabola, which can either open upwards if a > 0 or downwards if a < 0.Quadratic functions are essential because they model many real-world situations, like the path of a thrown ball or the area of a space. Understanding their properties, such as finding the vertex, axis of symmetry, and roots, is crucial for solving various mathematical problems.
vertex form
The vertex form of a quadratic function is a way to express the function to easily identify its vertex, which is the highest or lowest point on the graph (parabola). The vertex form is written as:f(x) = a(x - h)^2 + k.In this formula:
- 'a' determines the direction and width of the parabola.
- (h, k) defines the vertex of the parabola.
graph transformations
Graph transformations allow you to manipulate and shift the graph of a function without changing its fundamental shape.Transformations can include:
- Vertical Shifts: Moving the graph up or down without altering its shape. This affects the 'k' value in the vertex form.
- Horizontal Shifts: Moving the graph left or right. This affects the 'h' value in the vertex form.
- Reflections: Flipping the graph over the x-axis or y-axis, depending on the sign of 'a'.
- Vertical Stretch/Compression: Making the graph narrower or wider, controlled by the absolute value of 'a'.
parabola
A parabola is the U-shaped graph of a quadratic function. It can open upwards or downwards depending on the coefficient 'a' in the quadratic function:
- If a > 0, the parabola opens upwards.
- If a < 0, the parabola opens downwards.
- Vertex: The highest or lowest point of the parabola, given by (h, k) in the vertex form.
- Axis of Symmetry: A vertical line that divides the parabola into two mirror images, passing through the vertex at x = h.
- Focus: A point inside the parabola used to define its shape, found using the formula 1/(4a).
- Directrix: A line perpendicular to the axis of symmetry, located equidistant from the vertex as the focus, which helps in constructing the parabola using the definition.