BREAKING: Target Test Prep releases Brand New 2026 On Demand GMAT prep course

Redeem
TTP OnDemand GMAT Video Course
Featured Course

Target Test Prep GMAT OnDemand

Scott Woodbury-Stewart’s private virtual classroom — 400 hours of master-class video lessons for the GMAT Focus Edition.

  • 715+ score guarantee — highest in the industry (99th percentile)
  • 52 chapters · 1,500+ lessons · 4,000+ practice questions
  • 400 hours of video · 1,500+ instructor-led HD smartboard lessons
  • 300,000+ students accepted to Harvard, Stanford, Wharton, Booth & Sloan & more
  • 24/7 live support + weekly Zoom office hours with GMAT instructors
  • TTP AI Assist — 24/7 AI-powered virtual tutor for instant help
  • 1,200+ flashcards + AI-powered study assistant & daily calendar
  • OnDemand, LiveTeach & GMAT Bootcamp formats available
  • Also: GRE, SAT Math & Executive Assessment courses
  • MBA Admissions Consulting now available
  • 🏆 2025 EdTech Breakthrough Award: Test Prep Solution Provider of the Year
  • 200,000+ students served
  • 5-day free trial — $0 to start, no auto-billing, cancel anytime
★★★★★ 5.0 (559 reviews)
130-pt guarantee
$0 to start then $127/mo
Start Free 5-Day Trial Read 559 Reviews →

Graphing question

Expert replies
Post new topic Post Reply
Previous Topic Next Topic
Master | Next Rank: 500 Posts
Posts: 117
Joined: Fri Oct 17, 2008 7:41 am
by awilhelm » Sun Dec 14, 2008 8:34 pm
Please help with the following question:

In the xy-plane, at what two points does the graph of y = (x + a)(x + b) intersect the x-axis?

1) a + b = -1
2) The graph intersects the y-axis at (0, -6)

Thanks!
Top
Join the discussion
Log in to postLogin with Googleuse password
QUOTE IN REPLY
Source: — Data Sufficiency |
Senior | Next Rank: 100 Posts
Posts: 62
Joined: Thu Oct 23, 2008 9:20 am

Re: Graphing question

by tritrantran » Sun Dec 14, 2008 8:50 pm
awilhelm wrote:Please help with the following question:

In the xy-plane, at what two points does the graph of y = (x + a)(x + b) intersect the x-axis?

1) a + b = -1
2) The graph intersects the y-axis at (0, -6)

Thanks!
So when it intersects the x-axis, y = 0.

0 = (x+a)(x+b)
x = -a or x = -b

Statement (1)
a + b = -1
A and B could be multiple values....INSUFFICIENT

Statement (2)
The graph intersects the y-axis at (0, -6)
y = (x + a)(x + b)

-6 = (0+a)(0+b)
-6 = ab
A and B could be multiple values...INSUFFICIENT

St (1) and St (2)
a + b = -1
-6 = ab

-6 = (-1 - b)*b
-6 = -b - b^2
b^2+b-6 = 0

b= -3 or b = 2

If b = -3, then a = 2
If b = 2, then a = -3

y = (x+2)(x-3) or
y= (x-3)(x+2)


SUFFICIENT (C)
Last edited by tritrantran on Sun Dec 14, 2008 9:39 pm, edited 1 time in total.
Top
Join the discussion
Log in to postLogin with Googleuse password
QUOTE IN REPLY
Master | Next Rank: 500 Posts
Posts: 117
Joined: Fri Oct 17, 2008 7:41 am

by awilhelm » Sun Dec 14, 2008 8:55 pm
Thanks a lot!
Top
Join the discussion
Log in to postLogin with Googleuse password
QUOTE IN REPLY
Master | Next Rank: 500 Posts
Posts: 117
Joined: Fri Oct 17, 2008 7:41 am

by awilhelm » Sun Dec 14, 2008 9:17 pm
Near the end of your reply, you say:

b= -3 or b = 2

If b = -3, then a = 2
If b = -2, then a = 1 ( doesn't work -6 = ab)
So a = 2, b =-3

But why are you offering -2 as a possible value for b? The equations are:
-6 = ab
a + b = -1

So if b = -3, then a = 2
but if b = 2, then a = -3

We don't know which values for a and b are correct, no??
Top
Join the discussion
Log in to postLogin with Googleuse password
QUOTE IN REPLY
Senior | Next Rank: 100 Posts
Posts: 62
Joined: Thu Oct 23, 2008 9:20 am

by tritrantran » Sun Dec 14, 2008 9:37 pm
awilhelm wrote:Near the end of your reply, you say:

b= -3 or b = 2

If b = -3, then a = 2
If b = -2, then a = 1 ( doesn't work -6 = ab)
So a = 2, b =-3

But why are you offering -2 as a possible value for b? The equations are:
-6 = ab
a + b = -1

So if b = -3, then a = 2
but if b = 2, then a = -3

We don't know which values for a and b are correct, no??
My mistake...

So if b = -3, a = 2
or b =2, a = -3

y = (x+2)(x-3) or
y = (x-3)(x+2)

This is still the same equation (C)
Top
Join the discussion
Log in to postLogin with Googleuse password
QUOTE IN REPLY
Master | Next Rank: 500 Posts
Posts: 117
Joined: Fri Oct 17, 2008 7:41 am

by awilhelm » Sun Dec 14, 2008 9:51 pm
Got it, thanks again!
Top
Join the discussion
Log in to postLogin with Googleuse password
QUOTE IN REPLY
User avatar
Legendary Member
Posts: 546
Joined: Sun Nov 16, 2008 11:00 pm
Location: New Delhi , India
Thanked: 13 times

by ronniecoleman » Sun Dec 14, 2008 10:01 pm
IMO C
Admission champion, Hauz khaz
011-27565856
Top
Join the discussion
Log in to postLogin with Googleuse password
QUOTE IN REPLY
Post new topic Post Reply
• Page 1 of 1