Chapter 2: Problem 13
Describing Transformations Suppose the graph of \(f\) is given. Describe how the graph of each function can be obtained from the graph of \(f\) (a) \(y=-f(x)+5\) (b) \(y=3 f(x)-5\)
Short Answer
Expert verified
(a) Reflect over x-axis and shift 5 up. (b) Stretch vertically by 3, shift 5 down.
Step by step solution
01
Understanding Vertical Reflections
The term \(-f(x)\) indicates a reflection across the x-axis. This means that every point on the graph of \(f(x)\) will be reflected to the opposite side of the x-axis. If a point on \(f\) was above the x-axis, it will now be below by the same distance, and vice versa.
02
Apply Vertical Shift for (a)
The term \(+5\) in \(y=-f(x)+5\) corresponds to a vertical shift. Specifically, this transformation shifts the graph 5 units upward. So, after reflecting the graph across the x-axis, shift the entire graph upward by 5 units.
03
Reflection and Shift for Part (a)
For the function \(y=-f(x)+5\), apply the reflection over the x-axis and then shift the resulting graph 5 units up. This completes the transformation for part (a).
04
Understanding Vertical Stretch
The coefficient \(3\) in \(3f(x)\) represents a vertical stretch of the graph by a factor of 3. This means that the distance from any point on the graph to the x-axis will be multiplied by 3, making the graph taller if \(f(x)\) is positive, or more negative if \(f(x)\) is negative.
05
Apply Vertical Shift for (b)
The term \(-5\) in \(y=3f(x)-5\) indicates a vertical shift downward by 5 units. After stretching the graph vertically, shift every point downward by 5 units.
06
Stretch and Shift for Part (b)
For the function \(y=3f(x)-5\), apply a vertical stretch by a factor of 3 and then shift the entire graph 5 units down. This completes the transformation for part (b).
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Vertical Reflection
A vertical reflection in mathematics involves flipping the graph of a function over the x-axis. Imagine placing a mirror along the x-axis; the graph will mirror itself on the opposite side. If you have the function \(f(x)\), then \(-f(x)\) represents its vertical reflection. Here’s how it works:
- Every point (x, y) on the original graph is flipped to (x, -y).
- If a point was above the x-axis, it will now be below at the same distance.
- Similarly, if a point was below, it will move above, mirroring across the x-axis.
Vertical Shift
A vertical shift changes the function's position along the y-axis. When analyzing the function \(y = -f(x)+5\), the term \(+5\) indicates a vertical shift upwards by 5 units. Here’s the process for understanding vertical shifts:
- If the term is positive (e.g., +5), shift the graph upward by that many units.
- If the term is negative (e.g., -5), shift the graph downward.
- Vertical shifts do not affect the shape of the graph, only its position on the y-axis.
Vertical Stretch
A vertical stretch involves modifying the function's amplitude without altering its overall shape. When you multiply \(f(x)\) by a factor larger than 1, you stretch it away from the x-axis. For instance, in \(y = 3f(x)\), each point on the graph is extended three times further from the x-axis:
- The distance from each point to the x-axis increases by the factor, here 3 times.
- If \(f(x)\) is positive, the graph becomes taller. If it's negative, it stretches downwards.
- This transformation doesn’t shift the graph left or right, only alters the vertical dimension.