Find all School-related info fast with the new School-Specific MBA Forum

 It is currently 06 Jul 2015, 12:38

### GMAT Club Daily Prep

#### Thank you for using the timer - this advanced tool can estimate your performance and suggest more practice questions. We have subscribed you to Daily Prep Questions via email.

Customized
for You

we will pick new questions that match your level based on your Timer History

Track

every week, we’ll send you an estimated GMAT score based on your performance

Practice
Pays

we will pick new questions that match your level based on your Timer History

# Events & Promotions

###### Events & Promotions in June
Open Detailed Calendar

# What is the equation of the line that is perpendicular to

Author Message
TAGS:
CEO
Joined: 21 Jan 2007
Posts: 2760
Location: New York City
Followers: 9

Kudos [?]: 390 [0], given: 4

What is the equation of the line that is perpendicular to [#permalink]  21 Nov 2007, 05:28
00:00

Difficulty:

(N/A)

Question Stats:

0% (00:00) correct 0% (00:00) wrong based on 0 sessions
What is the equation of the line that is perpendicular to line y=2x and passes through point (a,b)?

1. a = -b
2. a - b = 1

Intern
Joined: 28 Aug 2007
Posts: 19
Location: London, United Kingdom
Followers: 1

Kudos [?]: 1 [0], given: 0

I'll give it a go...

The slope of a line perpendicular to another line is equal to minus the reciprocal of the slope of the line to which it is perpendicular.

Therefore the slope of the line perpendicular to y = 2x is -1/2

Therefore the equation of the perpendicular line is y = -1/2x + k

Statement 1: a = -b This is insufficient, as there are an infinite number of co-ordinates that match this criterion, e.g. (-1, 1), (1,-1), (2,-2), (-2,2), etc.

Statement 2: a - b = 1 This is insufficient, as again there are an infinite number of co-ordinates that match this criterion.

Statements 1 and 2 together: subsitute the equation in Statement 2 into the equation in Statement 1 and solve for b:
(1 + b) = -b
1 = -2b
b = -1/2

Subsitute into either equation to solve for a:

a = 1/2

Therefore the perpendicular line goes through co-ordinates (1/2; -1/2).

Substitute these co-ordinates into the equation of the perpendicular line and solve for k:

y = -1/2x + k

(-1/2) = -1/2(1/2) + k

-1/2 = -1/4 + k

- 2/4 + 1/4 = k

k = -1/4

Therefore equation of perpendicular line is y = -1/2x - 1/4

CEO
Joined: 21 Jan 2007
Posts: 2760
Location: New York City
Followers: 9

Kudos [?]: 390 [0], given: 4

OA is C.
Similar topics Replies Last post
Similar
Topics:
3 What are the equations of the two parallel lines shown here? 5 05 Jan 2013, 20:41
1 In the xy plane, what is the slope of line perpendicular to 2 28 Aug 2011, 11:33
What is the slope of the line 'L'? a) equation of line l is 2 03 Feb 2011, 12:18
5 In the xy – plane, what is the slope of line perpendicular 6 23 Jan 2011, 10:38
What is the equation of the line that is perpendicular to 3 01 Oct 2009, 07:25
Display posts from previous: Sort by