Lesson Objectives
- Learn how to reflect a graph across the x-axis
- Learn how to reflect a graph across the y-axis
How to Reflect a Graph Across an Axis
Another type of graphing transformation is a reflection. When we talk about a reflection, it can be thought of as a folding or flipping of the graph over the line of reflection. $$g(x)=-f(x)$$ g(x) is the graph of f(x) reflected across the x-axis. $$g(x)=f(-x)$$ g(x) is the graph of f(x) reflected across the y-axis. Let's look at an example.
Example #1: Describe the transformation from f(x) to g(x). $$f(x)=|x|$$ $$g(x)=-|x|$$ Since g(x) = -f(x), we can state that g(x) is the graph of f(x) reflected across the x-axis.
Example #1: Describe the transformation from f(x) to g(x). $$f(x)=|x|$$ $$g(x)=-|x|$$ Since g(x) = -f(x), we can state that g(x) is the graph of f(x) reflected across the x-axis.
Skills Check:
Example #1
Describe the transformation from f(x) to g(x). $$f(x)=\sqrt{x}$$ $$g(x)=\sqrt{-x}$$
Please choose the best answer.
A
Reflected across the y-axis
B
Reflected across the x-axis
Example #2
Describe the transformation from f(x) to g(x). $$f(x)=x^2$$ $$g(x)=-x^2$$
Please choose the best answer.
A
Reflected across the y-axis
B
Reflected across the x-axis
Example #3
Describe the transformation from f(x) to g(x). $$f(x)=x^4$$ $$g(x)=-x^4$$
Please choose the best answer.
A
Reflected across the y-axis
B
Reflected across the x-axis
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