GMAT Math : Graphing

Study concepts, example questions & explanations for GMAT Math

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Example Questions

Example Question #5 : Coordinate Geometry

Define a function  as follows:

Give the -intercept of the graph of .

Possible Answers:

The graph of  has no -intercept.

Correct answer:

The graph of  has no -intercept.

Explanation:

The -coordinate of the -intercept is :

However, the logarithm of a negative number is an undefined expression, so  is an undefined quantity, and the graph of  has no -intercept.

Example Question #6 : Coordinate Geometry

Define a function  as follows:

Give the equation of the vertical asymptote of the graph of .

Possible Answers:

Correct answer:

Explanation:

Only positive numbers have logarithms, so

The graph never crosses the vertical line of the equation , so this is the vertical asymptote. 

Example Question #7 : Coordinate Geometry

Define a function  as follows:

Give the equation of the vertical asymptote of the graph of .

Possible Answers:

The graph of  has no vertical asymptote.

Correct answer:

Explanation:

Only positive numbers have logarithms, so

The graph never crosses the vertical line of the equation , so this is the vertical asymptote. 

Example Question #8 : Coordinate Geometry

Define a function  as follows:

Give the -intercept of the graph of .

Possible Answers:

The graph of  has no -intercept.

Correct answer:

Explanation:

The -coordinate of the -intercept is :

Since 2 is the cube root of 8, , and  . Therefore, 

.

The -intercept is .

Example Question #9 : Coordinate Geometry

Define functions  and  as follows:

Give the -coordinate of a point at which the graphs of the functions intersect.

Possible Answers:

The graphs of  and  do not intersect.

Correct answer:

Explanation:

Since , the definition of  can be rewritten as follows:

First, we need to find the -coordinate of the point at which the graphs of  and  meet by setting 

Since the common logarithms of the polynomial and the rational expression are equal, we can set those expressions themselves equal, then solve:

We can solve using the  method, finding two integers whose sum is 24 and whose product is  - these integers are 10 and 14, so we split the niddle term, group, and factor: 

or 

This gives us two possible -coordinates. However, since 

,

an undefined quantity - negative numbers not having logarithms -

we throw this value out. As for the other -value, we evaluate: 

and 

 is the correct -value, and  is the correct -value.

Example Question #10 : Coordinate Geometry

Let  be the point of intersection of the graphs of these two equations:

Evaluate .

Possible Answers:

Correct answer:

Explanation:

Substitute  and  for  and , respectively, and solve the resulting system of linear equations:

Multiply the first equation by 2, and the second by 3, on both sides, then add:

            

Now back-solve:

We need to find both  and  to ensure a solution exists. By substituting back:

.

 

 is the solution, and , the correct choice.

 

Example Question #11 : Graphing

Let  be the point of intersection of the graphs of these two equations:

Evaluate .

Possible Answers:

The system has no solution.

Correct answer:

Explanation:

Substitute  and  for  and , respectively, and solve the resulting system of linear equations:

Multiply the first equation by 2, and the second by 3, on both sides, then add:

            

Back-solve:

We need to find both  and  to ensure a solution exists. By substituting back:

and

We check this solution in both equations:

 - true.

 

 - true.

 

 is the solution, and , the correct choice.

 

 

Example Question #12 : Graphing

The graph of function  has vertical asymptote . Which of the following could give a definition of  ?

Possible Answers:

Correct answer:

Explanation:

Given the function , the vertical asymptote can be found by observing that a logarithm cannot be taken of a number that is not positive. Therefore, it must hold that , or, equivalently,  and that the graph of  will never cross the vertical line . That makes  the vertical asymptote, so it follows that the graph with vertical asymptote  will have  in the  position. The only choice that meets this criterion is

Example Question #13 : Graphing

The graph of a function  has -intercept . Which of the following could be the definition of  ?

Possible Answers:

All of the other choices are correct.

Correct answer:

All of the other choices are correct.

Explanation:

All of the functions are of the form . To find the -intercept of such a function, we can set  and solve for :

Since we are looking for a function whose graph has -intercept , the equation here becomes , and we can examine each of the functions by finding the value of .

:

 

 

 

 

 

All four choices fit the criterion.

Example Question #14 : Graphing

The graph of a function  has -intercept . Which of the following could be the definition of  ?

Possible Answers:

Correct answer:

Explanation:

All of the functions take the form 

for some integer . To find the choice that has -intercept , set  and , and solve for :

In exponential form:

The correct choice is .

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