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General Mathematics - M04 - L04 - WEEK 1

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JC Excellente Christian Academy Inc.

ACADEMIC EXCELLENCE.LEADERSHIP POTENTIAL. CHRISTIAN VALUES


Blk. 40 Lot 73 Road 1 Minuyan II, CSJDM Bulacan

General Mathematics
2nd GRADING - WEEK 1
Module 4
Lesson 3

TOPIC: Graphing Transformations of Exponential Functions

INSTRUCTION:

Reflecting Graphs

Example #1: Use the graph of y=2x to graph the functions y=−2x and y=2−x .

Solution:
Some y-values are shown on the following table.

The y-coordinate of each point on the graph of y=– 2x the negative of the y-coordinate of the graph of y=2x .
Thus, the graph of y=– 2x is the reflection of the graph of y=2x about the x-axis.
The value of y=2−x at x is the same as the value of y=2x at – x. Thus, the graph of y=2−x is the reflection of the
graph of y=2x about the y-axis.

The corresponding graphs are shown below:

The results in Example #1 can be generalized as follows:


Reflection
 The graph of y=– f (x) is the reflection about the x-axis of the graph of y=f ( x ).
 The graph of y=f (– x) is the reflection about the y-axis of the graph of y=f ¿).

Example #2:
Use the graph of y=2x to graph the functions y=3 (2x ) and y=0.4(2 x ).

Solution:
Some y-values are shown on the following table.
The y-coordinate of each point on the graph of y=3 (2x ) is 3 times the y-coordinate of each point on y=2x .
Similarly, the y-coordinate of each point on the graph of y=0.4 ( 2 x ) is 0.4 times the y-coordinate of each point
on y=2x .

The graphs of these functions are shown below.

Observations:
1. The domain for all three graphs is the set of all real numbers.
2. The y-intercepts were also multiplied correspondingly. The y-intercept of y=3 (2x ) is 3, and the y-
intercept of y=0.4 ( 2 x ) is 0.4.
3. All three graphs have the same horizontal asymptote: y=0.
4. The range of all three graphs is the set of all y >0.

The results of Example #2 can be generalized as follows:


Vertical Stretching or Shrinking
Let c be a positive constant. The graph of y=cf ( x) can be obtained from the graph of y=f (x ) by multiplying
each y-coordinate by c. The effect is a vertical stretching (if c >1) or shrinking (if c <1) of the graph of y=f ( x ).

Example #3:
Use the graph of y=2x to graph y=2x – 3 and y=2x +1.

Solution:
Some y-values are shown on the following table:

The graphs of these functions are shown below:


Observations:
 The domain for all three graphs is the set of all real numbers.
 The y-intercepts and horizontal asymptotes were also vertically translated from the y-intercept and
horizontal asymptote of y=2x .
 The horizontal asymptote of y=2x is y=0. Shift this 1 unit up to get the horizontal asymptote of
y=2x +1 which is y=1, and 3 units down to get the horizontal asymptote of y=2x – 3 which is
y=– 3.
 The range of y=2x +1 is all y >1, and the range of y=2x – 3 is all y > – 3.

The results of Example #3 can be generalized as follows:


Vertical Shifts
Let k be a real number. The graph of y=f ( x )+ k is a vertical shift of k units up (if k > 0) or k units down (if k < 0
) of the graph of y=f (x ).

Example #4:
Use the graph of y=2x to graph y=2x−2and y=2x+ 4.

Solution.
Some y-values are shown on the following table.

The graphs of these functions are show below:

Observations:
 The domain for all three graphs is the set of all real numbers.
 The y-intercepts changed. To find them, substitute x=0 in the function. Thus, the y-intercept of
y=2x+ 4 is 24 =16 and the y-intercept of y=2x−2 is 2 – 2=.25.
 The horizontal asymptotes of all three graphs are the same ( y=0). Translating a graph horizontally does not
change the horizontal asymptote.
 The range of all three graphs is the set of all y >0 .

The results of Example #4 can be generalized as follows:


Horizontal Shifts
 Let k be a real number. The graph of y=f ( x – k ) is a horizontal shift of k units to the right (if k > 0) or k
units to the left (if k < 0) of the graph of y=f ( x ).
SOLVED EXAMPLES:

1. Sketch the graph of F (x)=3 x+1 – 2, then state the domain, range, y-intercept, and horizontal asymptote.

Solution:
Transformation:
The base function f (x)=3x will be shifted 1 unit to the left and 2 units down

Steps in Graph Sketching:


Step 1: Base function: f (x)=3x ; y-intercept: (0,1) ; horizontal asymptote: y=0
Step 2: The graph of F (x) is found by shifting the graph of the function f left one unit and down two units.
Step 3: The y-intercept of f (x) (0,1) will shift to the left by one unit and down two units towards ( – 1 , – 1).
This is not the y-intercept of F (x).
Step 4: The horizontal asymptote will be shifted down two units, which is y=– 2.
Step 5: Find additional points on the graph; F ( 0 )=30 +1 – 2 = 1 and F ( 1 )=3 1+1 – 2=7 .
Step 6: Connect the points using a smooth curve.

Domain: All real numbers


Range: (−2 , ∞)
y-intercept: (0,1)
Horizontal Asymptote: y=−2

EVALUATION:

Find the following for each of the given.


(a) use transformations to describe how the graph is related to its base exponential function y=b x,
(b) sketch the graph;
(c) identify its domain, range, y-intercept, and horizontal asymptote.

1. F ( x )=2 ( 3 x )

x+1
1
2. G ( x ) = ()4
−4

3. H ( x ) =−2(3 x−1 )

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