Chapter 3: Problem 12
Sketch the graph of the function and compare it with the graph of \(y=x^{2}\) \(y=-(x+3)^{2}-1\)
Short Answer
Expert verified
The graph of \(y=-(x+3)^{2}-1\) is a downward-opening parabola that is shifted 3 units to the left and 1 unit down compared to the graph of \(y=x^{2}\).
Step by step solution
01
Identify the shape of the base function
The base function in this exercise is \(y = x^{2}\). This is a parabola that opens upward, with the origin (0,0) as its vertex.
02
Identify the transformations
The function \(y=-(x+3)^{2}-1\) has three transformations applied to the base function: 1. The sign of x is changed, indicating a reflection across the y-axis.2. The \(x+3\) term represents a horizontal shift of the graph 3 units to the left.3. The -1 outside the square function represents a vertical shift down by 1 unit.4. The negative sign outside the square function indicates a reflection across the x-axis that flips the parabola so it opens downward.
03
Sketch the graph
Applying the above transformations to the base function \(y=x^{2}\) gives the graph of \(y=-(x+3)^{2}-1\). Start with the base function, then apply the transformations one by one. First, shift the graph to the left by 3 units, then move it down by 1 unit, and finally reflect it across the x-axis.
04
Compare with the original graph
The graph of \(y=-(x+3)^{2}-1\) is a downward-opening parabola that has been moved 3 units to the left and 1 unit down compared to the original graph of \(y=x^{2}\), which is an upward-opening parabola centered at the origin.
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Parabola Transformations
Parabola transformations involve modifying a standard parabola, which is typically represented as the function \(y = x^2\). These transformations allow us to change key features of the parabola, such as its direction, position, and shape. Transformations typically affect parabolas in the following ways:
- Direction of Opening: This refers to whether the parabola opens upwards or downwards. A positive coefficient in front of \(x^2\) opens upwards, while a negative coefficient opens downwards.
- Position: Position shifts can move the parabola left, right, up, or down, altering its vertex from the origin (0,0) to another location in the coordinate plane.
- Reflection: A reflection can occur across the x-axis or y-axis, effectively flipping the graph.
Reflection Across Axes
Reflecting a parabola across an axis changes its orientation. Let's break this down:
- Reflection across the x-axis: This flips the parabola upside down. For example, changing from \(y = x^2\) to \(y = -x^2\) reflects the graph across the x-axis, so it now opens downwards instead of upwards.
- Reflection across the y-axis: This type of reflection is less common with parabolas, as altering the sign inside the brackets, such as from \(y = (x)^2\) to \(y = (-x)^2\), doesn't affect the standard \(y = x^2\) function significantly in its basic form.
Horizontal Shift
Horizontal shifts move the parabola left or right along the x-axis. This shift is dictated by a constant added to or subtracted from the x-variable. Consider:
- Shift to the left: If the function includes \(x + c\), it signifies a shift of \(c\) units to the left. In our function \(y = -(x + 3)^2 - 1\), the \(+3\) moves the parabola 3 units to the left.
- Shift to the right: Conversely, if the function includes \(x - c\), that denotes a shift of \(c\) units to the right.
Vertical Shift
Vertical shifts involve moving the parabola up or down along the y-axis. This shift is achieved by adding or subtracting a constant outside the squared term. Here’s how it works:
- Shift upwards: By adding a constant \(d\), such as turning \(y = x^2\) into \(y = x^2 + d\), the entire graph lifts \(d\) units upwards.
- Shift downwards: Subtracting a number, as in the function \(y = -(x+3)^2 - 1\), pulls the parabola down by one unit from its current position. This is evident in the \(-1\) of the given function, moving the vertex of the parabola down on the y-axis.