Advanced Geometry : How to graph a function

Study concepts, example questions & explanations for Advanced Geometry

varsity tutors app store varsity tutors android store

Example Questions

Example Question #1 : How To Graph A Function

2

The figure above shows the graph of y = f(x). Which of the following is the graph of y = |f(x)|?

Possible Answers:

4

2

5

6

3

Correct answer:

2

Explanation:

One of the properties of taking an absolute value of a function is that the values are all made positive. The values themselves do not change; only their signs do. In this graph, none of the y-values are negative, so none of them would change. Thus the two graphs should be identical.

Example Question #3 : How To Graph A Function

Below is the graph of the function :

 

Which of the following could be the equation for ?

Possible Answers:

Correct answer:

Explanation:

First, because the graph consists of pieces that are straight lines, the function must include an absolute value, whose functions usually have a distinctive "V" shape. Thus, we can eliminate f(x) = x2 – 4x + 3 from our choices. Furthermore, functions with x2 terms are curved parabolas, and do not have straight line segments. This means that f(x) = |x2 – 4x| – 3 is not the correct choice. 

Next, let's examine f(x) = |2x – 6|. Because this function consists of an abolute value by itself, its graph will not have any negative values. An absolute value by itself will only yield non-negative numbers. Therefore, because the graph dips below the x-axis (which means f(x) has negative values), f(x) = |2x – 6| cannot be the correct answer. 

Next, we can analyze f(x) = |x – 1| – 2. Let's allow x to equal 1 and see what value we would obtain from f(1). 

f(1) = | 1 – 1 | – 2 = 0 – 2 = –2

However, the graph above shows that f(1) = –4. As a result, f(x) = |x – 1| – 2 cannot be the correct equation for the function. 

By process of elimination, the answer must be f(x) = |2x – 2| – 4. We can verify this by plugging in several values of x into this equation. For example f(1) = |2 – 2| – 4 = –4, which corresponds to the point (1, –4) on the graph above. Likewise, if we plug 3 or –1 into the equation f(x) = |2x – 2| – 4, we obtain zero, meaning that the graph should cross the x-axis at 3 and –1. According to the graph above, this is exactly what happens. 

The answer is f(x) = |2x – 2| – 4.

Example Question #1 : How To Graph A Function

Which of the following could be a value of f(x) for f(x)=-x^2 + 3?

Possible Answers:

6

3

7

5

4

Correct answer:

3

Explanation:

The graph is a down-opening parabola with a maximum of y=3. Therefore, there are no y values greater than this for this function.

Example Question #1 : Graphing

Screen_shot_2015-03-06_at_2.14.03_pm

What is the equation for the line pictured above?

Possible Answers:

Correct answer:

Explanation:

A line has the equation

 where  is the  intercept and  is the slope.

The  intercept can be found by noting the point where the line and the y-axis cross, in this case, at  so .

The slope can be found by selecting two points, for example, the y-intercept and the next point over that crosses an even point, for example, .

Now applying the slope formula,

 

 which yields .

Therefore the equation of the line becomes:

Example Question #1 : How To Graph A Function

Which of the following graphs represents the y-intercept of this function?

Possible Answers:

Function_graph_4

Function_graph_2

Function_graph_3

Function_graph_1

Correct answer:

Function_graph_1

Explanation:

Graphically, the y-intercept is the point at which the graph touches the y-axis.  Algebraically, it is the value of  when .

Here, we are given the function .  In order to calculate the y-intercept, set  equal to zero and solve for .

So the y-intercept is at .

Example Question #131 : Coordinate Geometry

Which of the following graphs represents the x-intercept of this function?

Possible Answers:

Function_graph_5

Function_graph_8

Function_graph_6

Function_graph_7

Correct answer:

Function_graph_6

Explanation:

Graphically, the x-intercept is the point at which the graph touches the x-axis.  Algebraically, it is the value of  for which .

Here, we are given the function .  In order to calculate the x-intercept, set  equal to zero and solve for .

So the x-intercept is at .

Example Question #1 : How To Graph A Function

Which of the following represents ?

Possible Answers:

Function_graph_12

Function_graph_9

Function_graph_11

Function_graph_10

Correct answer:

Function_graph_9

Explanation:

A line is defined by any two points on the line.  It is frequently simplest to calculate two points by substituting zero for x and solving for y, and by substituting zero for y and solving for x.

Let .  Then

So our first set of points (which is also the y-intercept) is 

Let .  Then

So our second set of points (which is also the x-intercept) is .

Example Question #1 : How To Graph A Function

Suppose

To obtain the graph of , shift the graph  a distance of  units              .

Possible Answers:

Upwards

To the left

To the right

Downwards

Up and right

Correct answer:

Upwards

Explanation:

There are four shifts of the graph y = f(x):

y = f(x) + c shifts the graph c units upwards.

y = f(x) – c shifts the graph c units downwards.

y = f(x + c) shifts the graph c units to the left.

y = f(x – c) shifts the graph c units to the right.

Example Question #11 : How To Graph A Function

Which graph accurately represents the following function:

Possible Answers:

Wrong answer 2

Correct graph

Wrong graph 4

Wrong graph 3

Wrong graph

Correct answer:

Correct graph

Explanation:

The first step in determining which graph is correct is finding the origin of the function. If both x and y are equal to 0, the coordinates of the origin would be . The second step is to determine whether the graph opens up or down. The x and y are both positive, so the parabola will open upwards. The correct graph will look like 

Correct graph

Example Question #11 : How To Graph A Function

Which of the following graphs represents

Which of the following graphs represents the function ?

Possible Answers:

Screen shot 2015 10 21 at 4.33.18 pm

Screen shot 2015 10 21 at 4.34.32 pm

Screen shot 2015 10 21 at 4.33.33 pm

Screen shot 2015 10 21 at 4.35.18 pm

Screen shot 2015 10 21 at 4.35.32 pm

Correct answer:

Screen shot 2015 10 21 at 4.33.18 pm

Explanation:

The easiest way to determine which graph belongs to the equation is to find the x-intercept, the slope, and if necessary the y-intercept as well.

This equation is written in  form, where b=y-intercept and m=slope.

Therefore we know that the slope equals , and the y-intercept is .

The x-intercept can be found by substituting 0 for y and solving the equation.

The x-intercept is .

The only graph that meets these standards is 

Screen shot 2015 10 21 at 4.33.18 pm

Learning Tools by Varsity Tutors