Chapter 2: Problem 39
Sketch the graph of the function, not by plotting points, but by starting with the graph of a standard function and applying transformations. $$y=3-\frac{1}{2}(x-1)^{2}$$
Short Answer
Expert verified
The graph is a downward-opening parabola, shifted right 1 unit, vertically compressed, and moved up 3 units.
Step by step solution
01
Identify the Base Function
The given function is \( y = 3 - \frac{1}{2}(x-1)^{2} \). The base function is\( y = x^2 \), which is a standard parabolic graph opening upwards.
02
Apply Horizontal Shift
The function \( (x-1)^2 \) indicates a horizontal shift. The graph of \( y = x^2 \) is shifted 1 unit to the right to get the graph of \( y = (x-1)^2 \).
03
Apply Vertical Stretch and Reflection
The expression \( -\frac{1}{2}(x-1)^2 \) implies a vertical stretch by a factor of \( \frac{1}{2} \) and a reflection over the x-axis. The graph of \( y = (x-1)^2 \) is compressed and flipped upside down to give \( y = -\frac{1}{2}(x-1)^2 \).
04
Apply Vertical Shift
Finally, the function \( y = 3 - \frac{1}{2}(x-1)^2 \) involves a vertical shift upwards by 3 units. Shift the graph of \( y = -\frac{1}{2}(x-1)^2 \) up by 3 units to get the final graph of the function.
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Quadratic Functions
In the realm of graph transformations, quadratic functions play a pivotal role. The standard quadratic function, represented by the equation \( y = x^2 \), outlines the simplest parabolic graph. This graph is characterized by its symmetrical bell shape, known as a parabola, that opens upwards with its vertex at the origin \((0, 0)\).
The basic properties of a quadratic function include:
The basic properties of a quadratic function include:
- Its graph is a parabola.
- The direction of the opening is upwards when the coefficient of \( x^2 \) is positive.
- The vertex represents either the maximum or minimum point of the parabola.
- The axis of symmetry is a vertical line that intersects the vertex.
Horizontal Shift
A key transformation in modifying quadratic functions is the horizontal shift. This shift involves moving the entire graph sideways along the x-axis without altering its shape. Mathematically, if you see an expression of the form \((x - h)^2\), it's a sign of a horizontal shift. The parameter \( h \) determines the direction and distance of this shift.
- If \( h \) is positive, the graph shifts to the right.
- If \( h \) is negative, the shift is to the left.
Vertical Stretch and Reflection
After shifting a graph horizontally, further transformations can include vertical stretches and reflections. These modifications adjust the height and orientation of the graph without affecting its horizontal position.
In the quadratic equation \( y = 3 - \frac{1}{2}(x-1)^2 \), the coefficient \(-\frac{1}{2}\) before \((x-1)^2\) plays a dual role:
In the quadratic equation \( y = 3 - \frac{1}{2}(x-1)^2 \), the coefficient \(-\frac{1}{2}\) before \((x-1)^2\) plays a dual role:
- The negative sign indicates a reflection over the x-axis, meaning the graph of the parabola flips upside down.
- The fraction \( \frac{1}{2} \) denotes a vertical stretch of factor \( \frac{1}{2} \), which also means a compression since it's less than 1. This makes the parabola appear wider compared to the graph of \( y = x^2 \).
Vertical Shift
Finally, vertical shifts play an essential role in positioning the graph vertically along the y-axis. This transformation involves moving the graph up or down without altering its shape. When looking at the equation \( y = a(x - h)^2 + k \), the constant \( k \) signals a vertical shift.
Vertical shifts are often the final step in graph transformations, setting the graph precisely in its intended vertical position.
- If \( k \) is positive, move the graph upwards.
- If \( k \) is negative, shift the graph downwards.
Vertical shifts are often the final step in graph transformations, setting the graph precisely in its intended vertical position.