Chapter 2: Problem 21
In exercises \(21-24,\) expand and graph the function. $$ f(x)=(x-1)^{2}-2 $$
Short Answer
Expert verified
Expand: \(f(x) = x^2 - 2x - 1\). Graph: Vertex at (1, -2), parabola opens upwards.
Step by step solution
01
Expand the Function
To expand the function, we need to apply the square formula. The given function is \(f(x) = (x-1)^2 - 2\). We start by expanding \((x-1)^2\):\[(x-1)^2 = x^2 - 2x + 1\]Substitute this back into the function:\[f(x) = x^2 - 2x + 1 - 2\]Simplify the expression to get:\[f(x) = x^2 - 2x - 1\]
02
Graph the Function
To graph the function \(f(x) = x^2 - 2x - 1\), we need to identify its key features. This is a quadratic function of the form \(ax^2 + bx + c\), where \(a = 1\), \(b = -2\), and \(c = -1\).1. **Vertex**: The vertex formula for a quadratic function is given by \(x = -\frac{b}{2a}\). For this function:\[x = -\frac{-2}{2(1)} = 1\]Substitute \(x = 1\) back into the function to find the y-coordinate of the vertex:\[f(1) = (1)^2 - 2(1) - 1 = -2\]So, the vertex is \((1, -2)\).2. **Axis of Symmetry**: The line \(x = 1\).3. **Y-intercept**: Set \(x = 0\) and solve for \(f(x)\):\[f(0) = (0)^2 - 2(0) - 1 = -1\]So, the y-intercept is \((0, -1)\).4. **Plot Points**: We already have the vertex and y-intercept. To better define the graph, calculate a few more points around these, such as \(x = -1\) and \(x = 2\). - For \(x = -1\): \(f(-1) = (-1)^2 - 2(-1) - 1 = 2\). - For \(x = 2\): \(f(2) = (2)^2 - 2(2) - 1 = -1\).5. **Graph**: On a coordinate plane, plot the vertex \((1, -2)\), y-intercept \((0, -1)\), and additional points \((-1, 2)\) and \((2, -1)\). Draw a symmetric parabola opening upwards through these points.
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Graphing Quadratic Functions
Graphing quadratic functions can be a straightforward process once you understand their structure. These functions are typically in the form \( f(x) = ax^2 + bx + c \). The graph of a quadratic function is a curve known as a parabola. To accurately plot a quadratic function, you will need to identify its key characteristics:
- Vertex: The highest or lowest point.
- Axis of Symmetry: A vertical line through the vertex.
- Direction: Depends on the coefficient \(a\); if \(a > 0\), the parabola opens upwards, and if \(a < 0\), it opens downwards.
- Y-intercept: Where the graph intersects the \(y\)-axis.
Vertex Form
The vertex form of a quadratic function helps to easily identify the vertex and analyze the graph. It is expressed as:\[ f(x) = a(x-h)^2 + k \]Here, \((h, k)\) represents the vertex of the parabola. The coefficient \(a\) determines the direction and width of the parabola.Converting a quadratic equation from standard form \(ax^2 + bx + c\) to vertex form involves completing the square, which provides more insight into the graph's behavior.
- Vertex: From the form \((h, k)\), find the coordinates.
- Direction: Sign of \(a\) informs if the parabola opens upwards or downwards.
Parabola
A parabola is the visual representation of a quadratic function and appears as a symmetric curved shape on a graph. Parabolas can open either upwards or downwards, giving them distinct properties:When graphing parabola:
- Identify the vertex: This is either the lowest or the highest point, depending on which way the parabola opens.
- Axis of symmetry: The parabola will mirror on this line, which passes through the vertex.
- Open direction: Controlled by the sign of the coefficient \(a\); if positive, the curve opens upward; if negative, downward.
- Slope: A greater (absolute) value of \(a\) causes a steeper parabola.
Axis of Symmetry
The axis of symmetry is an imaginary line that vertically divides a parabola into two symmetrical halves. It is a crucial feature in graphing quadratic functions. For a quadratic function in the form \(f(x) = ax^2 + bx + c\), the axis of symmetry can be calculated as:\[ x = -\frac{b}{2a} \]This line goes straight through the vertex of the parabola, ensuring that one side mirrors the other perfectly.Key points about the axis of symmetry:
- Informs about the vertex: The \(x\)-coordinate of the vertex lies on this line.
- Ease of graphing: Points plotted on one side of the axis can easily be mirrored onto the other side.