2 functions and their graphs
TRANSCRIPT
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2 Functions and Their Graphs
Copyright © Cengage Learning. All rights reserved.
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2.5 Transformations of Functions
Copyright © Cengage Learning. All rights reserved.
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Use rigid and nonrigid transformations to sketch graphs of
functions.
Rigid:
vertical shift (aka translation)
horizontal shift (aka translation)
reflection
These are called rigid transformations because the basic
shape of the graph is unchanged. These transformations
change only the position of the graph in the coordinate
plane.
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Objective
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Nonrigid:
vertical stretch
vertical shrink
horizontal stretch
horizontal shrink
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These are called nonrigid transformations because they
cause a distortion - a change in the shape of the original
graph.
Objective
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Rigid Transformations:
Shifting (Translating) Graphs
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Vertical and horizontal shifts generate a family of functions, each
with the same shape but at a different location in the plane.
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Shifting Graphs - Vertically
Many functions have graphs that are simple transformations
of the parent graphs.
For example, you can obtain
the graph of h(x) = x2 + 2
by shifting the graph of the parent
f(x) = x2 up two units.
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In function notation, h and f
are related as follows:
h(x) = x2 + 2 = f(x) +2
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Shifting Graphs - Horizontally
Similarly, you can obtain the
graph of g(x) = (x – 2)2
by shifting the graph of f(x) = x2
to the right two units.
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In this case, the functions
g and f have the following
relationship:
g(x) = (x – 2)2 = f(x – 2)
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Shifting Graphs - Vertically
Challenge:
Use the graph of f(x) = x3 to sketch
the graph of g(x) = x3 + 1
Solution:
Relative to the graph of f(x) = x3,
this graph is a upward shift
of one unit.
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Shifting Graphs
Use the graph of f(x) = x3 to sketch
the graph of g(x) = (x – 2)3
Shifting Graphs - Horizontally
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Shifting Graphs – Vertically OR Horizontally
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Shifting Graphs – Vertically OR Horizontally
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Shifting Graphs – Vertically OR Horizontally
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Shifting Graphs – Vertically OR Horizontally
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Shifting Graphs
CW # 1
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1. Use the graph of f(x) = x2 to sketch the graph of each function.
a. h(x) = x2 – 3 b. g(x) = (x + 1)2 – 2
2.
3. Use the graph of f(x) = 𝑥 to sketch the graph of each function.
a. h(x) = 𝑥 – 3 b. g(x) = 𝑥 − 3
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Some graphs can be obtained from combinations of vertical
AND horizontal shifts.
Challenge:
Use the graph of f(x) = x3 to sketch
the graph of h(x) = (x + 2)3 + 1
Solution:
Relative to the graph of f(x) = x3,
this graph involves a left shift of
two units and an upward shift of
one unit.
You obtain the same result
regardless of which shift comes first.
Shifting Graphs – Vertically AND Horizontally
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Shifting Graphs – Vertically AND Horizontally
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Shifting Graphs – Vertically AND Horizontally
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Shifting Graphs – Vertically AND Horizontally
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CW # 2
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Graph these.
Shifting Graphs – Vertically AND Horizontally
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Shifting Graphs – Vertically AND Horizontally
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Reflecting Graphs
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Another common type of transformation is a reflection.
Multiply it all by –1
Replace x with –x
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Reflections across x
For instance, if you consider the
x-axis to be a mirror, the graph of
h(x) = –x2
is the mirror image (or reflection)
of the graph of
f(x) = x2
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Challenge: Compare the graph of 𝑔 𝑥 = − 𝑥 with 𝑓 𝑥 = 𝑥
Solution: The graph of g is a reflection of the graph of f in
the x-axis…
Algebraically:
𝑔 𝑥 = − 𝑥= −𝑓(𝑥)
Graphically:
ReflectionsReflections across x
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ReflectionsReflections across x
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ReflectionsReflections across x
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Reflections across y
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Reflections across y
Which of these other functions can
also be reflected across the y-axis?
CW # 3
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Vertical, Horizontal, and/or Reflection
To summarize:
There are three changes that can be made.
1) Adding or subtracting at the end causes a vertical shift.
2) Replacing the x with (x ± c) causes a horizontal shift.
3) Multiplying the x portion by –1 causes a reflection.
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Vertical, Horizontal, and/or Reflection
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CW # 4Graph these functions.
Vertical, Horizontal, and/or Reflection
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Vertical, Horizontal, and/or Reflection
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Writing Equations From Graphs
CW # 5
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Writing Equations From Graphs
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Nonrigid Transformations
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These cause a distortion - a change in the shape of the original graph.
A nonrigid transformation of the graph of y = f(x) is represented
by g(x) = c · f(x), where the transformation is a vertical stretch
when c > 1 and a vertical shrink if 0 < c < 1.
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Compare the graph of h(x) = 3|x |
with the graph of f(x) = |x |.
Relative to the graph of f(x) = |x |,
the graph of h(x) = 3|x | = 3 · f(x)
is a vertical stretch (each y-value
is multiplied by 3) of the graph of f.
Vertical Stretch
A nonrigid transformation of the graph of y = f(x) is represented
by g(x) = c · f(x), where the transformation is a vertical stretch
when c > 1 and a vertical shrink if 0 < c < 1.
In other words, multiply the function by a constant.
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Compare the graph of g(x) = ⅓|x | with the graph of f(x) = |x |.
Relative to the graph of f(x) = |x |,
the graph of g(x) = ⅓|x | = ⅓ · f(x)
is a vertical shrink (each y-value
is multiplied by ⅓) of the graph of f.
Vertical Shrink
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Vertical Stretch and Shrink
Combined
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Vertical StretchVertical Stretch and Shrink
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Vertical Stretch and Shrink
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Another nonrigid transformation of the graph of y = f(x) is
represented by h(x) = f · (cx), where the transformation is a
horizontal shrink when c > 1 and a horizontal stretch
when 0 < c < 1.
In other words, replace x with c · x.
Horizontal Stretch and Shrink
Compare the graph of g(x) = f(2x)
with the graph of f(x) = 2 – x3.
Relative to the graph of f(x) = 2 – x3,
the graph of
g(x) = f(2x) = 2 – (2x)3 = 2 – 8x3
is a horizontal shrink (c > 1).
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Horizontal Stretch and Shrink
Compare the graph of h(x) = f(½x) with the graph of f(x) = 2 – x3.
Relative to the graph of f(x) = 2 – x3,
the graph of
h(x) = f(½x) = 2 – (½x)3 = 2 –1
8x3
is a horizontal stretch (0 < c < 1).
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Horizontal Stretch and Shrink
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Horizontal Stretch and Shrink
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Horizontal Stretch and Shrink
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Horizontal Stretch and Shrink
Different functions, same results. Why?
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Vertical and Horizontal, Stretch and Shrink
CW # 6
For each of the above: Is it a Vertical Stretch, Vertical Shrink,
Horizontal Stretch, or a Horizontal Shrink?