GMAT Math : Geometry

Study concepts, example questions & explanations for GMAT Math

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Example Questions

Example Question #1 : Graphing A Quadratic Function

 has as its graph a vertical parabola on the coordinate plane. You are given that  and , but you are not given .

Which of the following can you determine without knowing the value of  ?

I) Whether the graph is concave upward or concave downward

II) The location of the vertex

III) The location of the -intercept

IV) The locations of the -intercepts, if there are any

V) The equation of the line of symmetry

Possible Answers:

I, III, and IV only

I, II, and V only

I and V only

I and III only

III and IV only

Correct answer:

I and III only

Explanation:

I) The orientation of the parabola is determined solely by the sign of . Since , the parabola can be determined to be concave downward.

II and V) The -coordinate of the vertex is ; since you are not given , you cannot find this. Also, since the line of symmetry has equation , for the same reason, you cannot find this either.

III) The -intercept is the point at which ; by substitution, it can be found to be at  known to be equal to 9, so the -intercept can be determined to be .

IV) The -intercept(s), if any, are the point(s) at which . This is solvable using the quadratic formula

Since all three of  and  must be known for this to be evaluated, and only  is known, the -intercept(s) cannot be identified.

The correct response is I and III only.

Example Question #151 : Advanced Geometry

Which of the following equations can be graphed with a vertical parabola with exactly one -intercept?

Possible Answers:

Correct answer:

Explanation:

The graph of  has exactly one -intercept if and only if 

 

has exactly one solution - or equivalently, if and only if

Since in all three equations, , we find the value of  that makes this statement true by substituting and solving:

The correct choice is .

Example Question #62 : Graphing

Give the vertex of the graph of the function 

.

Possible Answers:

Correct answer:

Explanation:

This can be answered rewriting this expression in the form 

.

Once this is done, we can identify the vertex as the point .

 

The vertex is 

 

 

Example Question #1001 : Problem Solving Questions

 has as its graph a vertical parabola on the coordinate plane. You are given that  and , but you are not given the value of .

Which of the following can you determine without knowing the value of  ?

I) Whether the graph is concave upward or concave downward

II) The location of the vertex

III) The location of the -intercept

IV) The locations of the -intercepts, if there are any

V) The equation of the line of symmetry

Possible Answers:

I, II, and V only

II and V only

III and IV only

I, III, and IV only

I and V only

Correct answer:

I and V only

Explanation:

I) The orientation of the parabola is determined solely by the sign of . Since , a positive value, the parabola can be determined to be concave upward.

II) The -coordinate of the vertex is ; since you given both  and , you can find this to be

The -coordinate is equal to . However, you need the entire equation to determine this value; since you do not know , you cannot find the -coordinate. Therefore, you cannot find the vertex.

 

III) The -intercept is the point at which ; by substitution, it can be found to be at  is unknown, so the -intercept cannot be found.

IV) The -intercept(s), if any, are the point(s) at which . This is solvable using the quadratic formula

Since all three of  and  must be known for this to be evaluated, and  is unknown, the -intercept(s) cannot be identified.

V) The line of symmetry has equation . When exploring the vertex, we found that this value is equal to , so the line of symmetry is the line of the equation .

The correct response is I and V only.

Example Question #1002 : Problem Solving Questions

 has as its graph a vertical parabola on the coordinate plane. You are given that , but you are given no other information about these values.

Which of the following can you determine without knowing the value of  ?

I) Whether the graph is concave upward or concave downward

II) The location of the vertex

III) The location of the -intercept

IV) The locations of the -intercepts,or whether there are any

V) The equation of the line of symmetry

Possible Answers:

 I, II, IV, and V only

II and V only

 I, IV, and V only

IV and V only

II, IV, and V only

Correct answer:

 I, IV, and V only

Explanation:

I) The orientation of the parabola is determined solely by the sign of . It is given in the problem that  is negative, so it follows that the parabola is concave downward.

II) The -coordinate of the vertex is ; since , this number is . The -coordinate is , but since we do not know the values of , and , we cannot find this value. Therefore, we cannot know the vertex.

III) The -intercept is the point at which ; by substitution, it can be found to be at  is unknown, so the -intercept cannot be found.

IV) The -intercept(s), if any, are the point(s) at which . This is solvable using the quadratic formula

Since , this can be rewritten and simplified as follows:

However, since  has no real square root,  has no real solutions, and its graph has no -intercepts.

V) The line of symmetry has equation . When exploring the vertex, we found that this value is equal to , so the line of symmetry is the line of the equation .

The correct response is I, IV, and V only.

Example Question #1003 : Problem Solving Questions

The graphs of the functions  and  have the same pair of -intercepts.

If we define , which of the following is a possible definition of  ?

Possible Answers:

Correct answer:

Explanation:

The -intercepts of the parabola 

can be determined by setting  and solving for :

 or 

The intercepts of the parabola are  and 

We can check each equation to see whether these two ordered pairs satisfy them.

 

:

 

 

 

 

Each of these equations has a parabola that does not have  as an -intercept. However, we look at 

 and  are also  -intercepts of the graph of this function, so this is the correct choice.

 

 

 

Example Question #1001 : Gmat Quantitative Reasoning

A vertical parabola has two -intercepts, one at   and one at .

Which of the following must be true about this parabola?

Possible Answers:

The parabola must have its -intercept at .

The parabola must have  as its vertex.

The parabola must be concave downward.

None of the statements in the other choices must be true.

The parabola must have the line of the equation  as its line of symmetry.

Correct answer:

The parabola must have the line of the equation  as its line of symmetry.

Explanation:

A parabola with its -intercepts at   and at  has as its equation

 

for some nonzero . If this is multiplied out, the equation can be rewritten as

or, simplified,

The sign of quadratic coefficient  determines whether it is concave upward or concave downward. We do not have the sign or any way of determining it.

The -coordinate of the -intercept is the contant, , but without knowing , we have no way of knowing .

The -coordinate of the vertex of   is the value . since , this expression becomes

The -coordinate is 

,

but without knowing , this coordinate, and the vertex itself, cannot be determined.

The line of symmetry is the line ; this value was computed to be equal to 6, so the line can be determined to be .

Example Question #1005 : Problem Solving Questions

Which of the following is the equation of the line of symmetry of a vertical parabola on the coordinate plane with its vertex at  ?

Possible Answers:

Correct answer:

Explanation:

The line of symmetry of a vertical parabola is a vertical line, the equation of which takes the form  for some . The line of symmetry passes through the vertex, which here is , so the equation must be .

Example Question #1006 : Problem Solving Questions

Which of the following is the equation of the line of symmetry of a horizontal parabola on the coordinate plane with its vertex at  ?

Possible Answers:

Correct answer:

Explanation:

The line of symmetry of a horizontal parabola is a horizontal line, the equation of which takes the form  for some . The line of symmetry passes through the vertex, which here is , so the equation must be .

Example Question #761 : Geometry

The graphs of the functions  and  have the same -intercept.

If we define , which of the following is a possible definition of  ?

Possible Answers:

Correct answer:

Explanation:

The -coordinate of the -intercept of the graph of a function of the form  - a quadratic function - is the point . Since , the -intercept is at the point .

Because of this, the graph of  has its -intercept at . Among the other choices, only  has a graph with its -intercept also at .

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