GMAT Question of the Day - Daily to your Mailbox; hard ones only

It is currently 17 Jun 2018, 15:23

Close

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
Your Progress

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

Not interested in getting valuable practice questions and articles delivered to your email? No problem, unsubscribe here.

Close

Request Expert Reply

Confirm Cancel

Events & Promotions

Events & Promotions in June
Open Detailed Calendar

If b, c, and d are constants and x^2 + bx + c = (x +

  new topic post reply Question banks Downloads My Bookmarks Reviews Important topics  
Author Message
TAGS:

Hide Tags

1 KUDOS received
Manager
Manager
User avatar
B
Joined: 16 Jan 2011
Posts: 102
If b, c, and d are constants and x^2 + bx + c = (x + [#permalink]

Show Tags

New post 05 Aug 2011, 06:16
1
7
00:00
A
B
C
D
E

Difficulty:

  75% (hard)

Question Stats:

45% (01:03) correct 55% (01:22) wrong based on 217 sessions

HideShow timer Statistics

If b, c, and d are constants and \(x^2 + bx + c = (x + d)^2\) for all values of x, what is the value of c?

(1) d = 3
(2) b = 6
Intern
Intern
User avatar
Status: If I play my cards right, I can work this to my advantage
Joined: 18 Jul 2011
Posts: 14
Location: India
Concentration: Operations, Social Entrepreneurship
GMAT Date: 11-12-2011
WE: Information Technology (Telecommunications)
Re: If b, c, and d are constants and x^2 + bx + c = (x + [#permalink]

Show Tags

New post 05 Aug 2011, 07:21
2
Galiya wrote:
If b, c, and d are constants and \(x^2 + bx + c = (x + d)^2\) for all values of x, what is the value
of c?
(1) d = 3
(2) b = 6

Spoiler: :: Comment
I got A instead of OA D
could you explain me please why it so?


ok here is what i think is the reasoning ...

expand the eqn .. \(x^2 + bx + c = x^2 + 2dx + d^2\)

cancelling the first term and comparing like terms we get

\(bx = 2dx << i.e. >>

b=2d\)

and \(c = d^2\)

now check the options we'd get both A and B to suffice ....
1 KUDOS received
Math Forum Moderator
avatar
Joined: 20 Dec 2010
Posts: 1901
Re: If b, c, and d are constants and x^2 + bx + c = (x + [#permalink]

Show Tags

New post 05 Aug 2011, 07:32
1
3
Galiya wrote:
If b, c, and d are constants and \(x^2 + bx + c = (x + d)^2\) for all values of x, what is the value
of c?
(1) d = 3
(2) b = 6


\(x^2 + bx + c = (x + d)^2\)

\(x^2 + bx + c = x^2 + d^2 + 2xd\) {:Note: (a+b)^2=a^2+b^2+2ab}

\(bx + c = d^2 + 2xd\) {:Note: (a+b)^2=a^2+b^2+2ab}


(1) d=3

\(bx + c = 9 + 6x\)

LHS=RHS for all x;

So, for x=0

\(b*0 + c = 9 + 6*0\)

\(c = 9\)

Sufficient.

(2) b=6

\(bx + c = d^2 + 2xd\)

LHS=RHS for all x;

So, for x=0

\(c=d^2\)----------1

for x=1

\(b + c = d^2 + 2d\)---------2

Using 1 and 2:
\(b = 2d\)

\(6=2d\)

\(d=3\)

Using 1:
\(c=d^2=3^2=9\)
Sufficient.

Ans: "D"
_________________

~fluke

GMAT Club Premium Membership - big benefits and savings

Manager
Manager
avatar
B
Joined: 30 Jul 2014
Posts: 145
GPA: 3.72
Reviews Badge
Re: If b, c, and d are constants and x^2 + bx + c = (x + [#permalink]

Show Tags

New post 12 Sep 2017, 05:27
fortunetellerz wrote:
Galiya wrote:
If b, c, and d are constants and \(x^2 + bx + c = (x + d)^2\) for all values of x, what is the value
of c?
(1) d = 3
(2) b = 6

Spoiler: :: Comment
I got A instead of OA D
could you explain me please why it so?


ok here is what i think is the reasoning ...

expand the eqn .. \(x^2 + bx + c = x^2 + 2dx + d^2\)

cancelling the first term and comparing like terms we get

\(bx = 2dx << i.e. >>

b=2d\)

and \(c = d^2\)

now check the options we'd get both A and B to suffice ....


Good to know - thanks. I forgot this strategy while solving the question.
_________________

A lot needs to be learned from all of you.

Re: If b, c, and d are constants and x^2 + bx + c = (x +   [#permalink] 12 Sep 2017, 05:27
Display posts from previous: Sort by

If b, c, and d are constants and x^2 + bx + c = (x +

  new topic post reply Question banks Downloads My Bookmarks Reviews Important topics  


cron

GMAT Club MBA Forum Home| About| Terms and Conditions and Privacy Policy| GMAT Club Rules| Contact| Sitemap

Powered by phpBB © phpBB Group | Emoji artwork provided by EmojiOne

Kindly note that the GMAT® test is a registered trademark of the Graduate Management Admission Council®, and this site has neither been reviewed nor endorsed by GMAC®.