# 11.07 Comparing function types

Lesson

We sometimes need to compare the behavior of two different functions, perhaps over a particular domain interval.

We may do this by looking at the graphs of the functions, by comparing tables of values of the functions or by examining the algebraic representations of the functions.

Questions we may wish to answer in comparing two functions include such things as

• Whether one function is always greater than or less than the other,
• Whether the graphs intersect and if so how often,
• Whether one or both functions are strictly increasing or decreasing on an interval,
• How the function values compare at selected points in the domain,
• How the slopes differ, and
• How the maximum or minimum values compare.

#### Practice questions

##### QUESTION 1

Consider the line $P$P given by the equation $y=-12+\frac{x}{10}$y=12+x10, and the table of values for parabola $Q$Q.

Parabola $Q$Q:

 $x$x $y$y $-8$−8 $-7$−7 $-6$−6 $-5$−5 $-4$−4 $-1$−1 $-4$−4 $-5$−5 $-4$−4 $-1$−1
1. Line $P$P is shown below. Draw the graph of the parabola $Q$Q.

2. How many times do $P$P and $Q$Q intersect?

Twice

A

Three times

B

Zero times

C

Once

D

Twice

A

Three times

B

Zero times

C

Once

D
3. Which function has the higher function value at the $y$y-intercept?

$Q$Q

A

$P$P

B

$Q$Q

A

$P$P

B
4. Which function has the higher function value at $x=-1$x=1?

$Q$Q

A

$P$P

B

$Q$Q

A

$P$P

B

##### QUESTION 2

The graph of the parabola $P$P, given by $y=\left(x-5\right)^2+5$y=(x5)2+5 is shown below.

1. Graph the parabola $Q$Q given by the equation $y=-2\left(x-7\right)\left(x-3\right)$y=2(x7)(x3).

2. By referring to the graphs, which function has a maximum at $y=8$y=8?

$P$P

A

$Q$Q

B

$P$P and $Q$Q

C

Neither $P$P or $Q$Q

D

$P$P

A

$Q$Q

B

$P$P and $Q$Q

C

Neither $P$P or $Q$Q

D
3. By referring to the graphs, which function has a minimum at $y=5$y=5?

$P$P

A

$Q$Q

B

$P$P and $Q$Q

C

Neither $P$P or $Q$Q

D

$P$P

A

$Q$Q

B

$P$P and $Q$Q

C

Neither $P$P or $Q$Q

D
4. Complete the following statements:

Parabola $P$P has $\editable{}$ zero(s).

Parabola $Q$Q has $\editable{}$ zero(s).

5. How many times do the parabolas intersect?

Once

A

Twice

B

Three times

C

Zero times

D

Once

A

Twice

B

Three times

C

Zero times

D

##### QUESTION 3

The graph of the exponential function $P$P, given by $y=4^{-x}$y=4x is shown below.

1. Graph the line $Q$Q given by the equation $y=8x+12$y=8x+12.

2. How many times do $P$P and $Q$Q intersect?

Zero times

A

Twice

B

Three times

C

Once

D

Zero times

A

Twice

B

Three times

C

Once

D
3. Which function has the higher function value at the $y$y-intercept?

$P$P

A

$Q$Q

B

$P$P

A

$Q$Q

B
4. Which function has the higher function value at $x=1$x=1?

$P$P

A

$Q$Q

B

$P$P

A

$Q$Q

B

### Outcomes

#### F.IF.C.9'''

Compare properties of two functions each represented in a different way (algebraically, graphically, numerically in tables, or by verbal descriptions). '''Include rational and radical; Focus on using key features to guide selection of appropriate type of model function