GEOMETRY

Expert replies

charmaine: Senior | Next Rank: 100 Posts; Posts: 71; Joined: Sun May 18, 2008 11:04 pm; Thanked: 1 times

by charmaine » Tue Sep 16, 2008 4:30 pm

which of the following lines is perpendicular to y =-2x+3 and h the same y intercept as y=2x-3 ?

can anyone explain ..thanks

[spoiler]ans. y=1/2x-3[/spoiler]

Like this post

Source: Beat The GMAT — Problem Solving | Tue Sep 16, 2008 4:30 pm

tendays2go: Senior | Next Rank: 100 Posts; Posts: 55; Joined: Sun Sep 14, 2008 6:51 am; Location: Netherlands; Thanked: 10 times; GMAT Score:680

by tendays2go » Wed Sep 17, 2008 12:48 am

it is:
y =1/2x - 3

as for two lines to be perpendicular, their slopes should multiply to -1
and the intercept on y axis for the second line is -3, when x is zero

thus, going by the eqn: y= mx+c
we have y =1/2x -3 or 2y = x - 6

Like this post

GMAT/MBA Expert

lunarpower: GMAT Instructor; Posts: 3380; Joined: Mon Mar 03, 2008 1:20 amFollowed by: 1535 members; Thanked: 2256 times; GMAT Score:800

by lunarpower » Thu Sep 18, 2008 1:17 am

tendays2go wrote:as for two lines to be perpendicular, their slopes should multiply to -1

yes.

a more functional way to think of this is that the slopes should be OPPOSITE RECIPROCALS of each other.
in other words, you take the fraction that represents the slope, flip the fraction, and change the sign.

since you want a line that's perpendicular to a line with a slope of -2 (= -2/1), you want a slope of +1/2.

Ron has been teaching various standardized tests for 20 years.

--

Pueden hacerle preguntas a Ron en castellano
Potete chiedere domande a Ron in italiano
On peut poser des questions Ã Ron en franÃ§ais
Voit esittÃ¤Ã¤ kysymyksiÃ¤ Ron:lle myÃ¶s suomeksi

--

Quand on se sent bien dans un vÃªtement, tout peut arriver. Un bon vÃªtement, c'est un passeport pour le bonheur.

Yves Saint-Laurent

--

Learn more about ron

Like this post

Post new topic Post Reply

• Page 1 of 1

GMAT Course Reviews

560 reviews

1168 reviews

431 reviews

359 reviews

147 reviews

5/5

5 Star (560 Reviews)

"Target Test Prep is the closest to the official version of the GMAT exam, about 99% accuracy in terms of the quality and quantity of information. The course has excellently created singular sets of focused lessons and tests for every possible topic that one could come across in the official GMAT exam."

"The TTP course maximizes the efficiency of the time you spend studying. It will take time and effort but I could almost guarantee that if you complete the course exactly as it is laid out you will get an amazing score. They also have a very responsive team willing to help with any questions you might have."

"TTP has two things that I think no other test prep company offers: A teaching approach that reinforces understanding and an attitude that will give you the mental preparedness needed to succeed on the test. TTP gives you a deep understanding of the concept you need to know while teaching you how to think."

Write a Review