GRE Math : Lines

Study concepts, example questions & explanations for GRE Math

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Example Questions

Example Question #1 : How To Find The Equation Of A Parallel Line

If the line through the points (5, –3) and (–2, p) is parallel to the line y = –2x – 3, what is the value of p ?

Possible Answers:

10

0

4

11

17

Correct answer:

11

Explanation:

Since the lines are parallel, the slopes must be the same. Therefore, (p+3) divided by (25) must equal 2. 11 is the only choice that makes that equation true. This can be solved by setting up the equation and solving for p, or by plugging in the other answer choices for p. 

Example Question #5 : How To Find The Equation Of A Parallel Line

Which of these formulas could be a formula for a line perpendicular to the line ?

Possible Answers:

Correct answer:

Explanation:

This is a two-step problem. First, the slope of the original line needs to be found. The slope will be represented by "" when the line is in -intercept form .

So the slope of the original line is . A line with perpendicular slope will have a slope that is the inverse reciprocal of the original. So in this case, the slope would be . The second step is finding which line will give you that slope. For the correct answer, we find the following:

So, the slope is , and this line is perpendicular to the original.

Example Question #11 : Parallel Lines

What is the equation for the line running through  and parallel to ?

Possible Answers:

Correct answer:

Explanation:

To begin, solve the given equation for .  This will give you the slope-intercept form of the line.

Divide everything by :

Therefore, the slope of the line is .

Now, for a point , the point-slope form of a line is:

, where  is the slope

For our point, this is:

This is the same as:

Distribute and solve for :

Example Question #13 : Coordinate Geometry

Quantity A: The slope of a line parallel to 

Quantity B: The slope of a line perpendicular to 

Which of the following is true?

Possible Answers:

The relationship between the quantities cannot be determined from the information provided.

Quantity B is larger.

Quantity A is larger. 

The two quantities are equal.

Correct answer:

Quantity B is larger.

Explanation:

For a question like this, it is easiest to start by putting each equation into the slope-intercept form.  This is , where  is the slope of the line.

 

Quantity A

Divide both sides by :

So, Quantity A is .  Parallel lines have equal slopes.

 

Quantity B

Divide both sides by :

Now, the perpendicular of a line has a slope that is opposite and reciprocal.  Therefore, the slope for Quantity B is .  This is a smaller negative number than the value for Quantity A. Therefore, absolutely speaking, it is a larger value. Therefore, Quantity B is larger.

Example Question #14 : Coordinate Geometry

Quantity A: The slope of the line parallel to 

Quantity B: The slope of the line parallel to 

Which of the following is true?

Possible Answers:

The two quantities are equal.

Quantity B is larger.

The relationship between the quantities cannot be determined for the information given.

Quantity A is larger.

Correct answer:

Quantity A is larger.

Explanation:

To begin, put each equation into slope-intercept form, which is .  The value for  is the slope of the line. The lines that are parallel to each of our given lines will have equal slopes to their respective lines. (Parallel lines have equal slopes, after all.)  

 

Quantity A

Divide both sides by :

Therefore, the slope of the line parallel to this one is .

 

Quantity B

Divide both sides by :

Therefore, the slope of the line parallel to this one is .  Therefore, Quantity A is larger.

Example Question #1 : How To Find The Slope Of Parallel Lines

What is the slope of a line parallel to the line: -15x + 5y = 30 ?

 

Possible Answers:

1/3

30

3

-15

Correct answer:

3

Explanation:

First, put the equation in slope-intercept form: y = 3x + 6. From there we can see the slope of this line is 3 and since the slope of any line parallel to another line is the same, the slope will also be 3.

 

 

 

 

 

 

Example Question #11 : Parallel Lines

What is the slope of any line parallel to –6x + 5y = 12?

Possible Answers:

6

12

12/5

5/6

6/5

Correct answer:

6/5

Explanation:

This problem requires an understanding of the makeup of an equation of a line.  This problem gives an equation of a line in y = mx + b form, but we will need to algebraically manipulate the equation to determine its slope.  Once we have determined the slope of the line given we can determine the slope of any line parallel to it, becasue parallel lines have identical slopes.  By dividing both sides of the equation by 5, we are able to obtain an equation for this line that is in a more recognizable y = mx + b form. The equation of the line then becomes y = 6/5x + 12/5, we can see that the slope of this line is 6/5.  

Example Question #3 : How To Find The Slope Of Parallel Lines

 

What is the slope of a line that is parallel to the line 11x + 4y - 2 = 9 – 4x  ?

 

 

Possible Answers:

Correct answer:

Explanation:

We rearrange the line to express it in slope intercept form.

Any line parallel to this original line will have the same slope.

 

             

 

 

 

Example Question #21 : Parallel Lines

In the standard (x, y) coordinate plane, what is the slope of a line parallel to the line with equation ?

Possible Answers:

Correct answer:

Explanation:

Parallel lines will have equal slopes. To solve, we simply need to rearrange the given equation into slope-intercept form to find its slope.

The slope of the given line is . Any lines that run parallel to the given line will also have a slope of .

Example Question #1 : How To Find The Slope Of Parallel Lines

What is the slope of a line that is parallel to the line ?

Possible Answers:

Correct answer:

Explanation:

Parallel lines have the same slope. The question requires you to find the slope of the given function. The best way to do this is to put the equation in slope-intercept form (y = mx + b) by solving for y.

First subtract 6x on both sides to get 3y = –6x + 12.

Then divide each term by 3 to get y = –2x + 4.

In the form y = mx + b, m represents the slope. So the coefficient of the x term is the slope, and –2 is the correct answer. 

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