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

It is currently 18 Jun 2019, 06:02

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

(n+k)^2 - 2nk =

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

Hide Tags

 
Senior PS Moderator
User avatar
V
Joined: 26 Feb 2016
Posts: 3373
Location: India
GPA: 3.12
(n+k)^2 - 2nk =  [#permalink]

Show Tags

New post 30 Oct 2018, 00:23
00:00
A
B
C
D
E

Difficulty:

  5% (low)

Question Stats:

100% (00:31) correct 0% (00:00) wrong based on 35 sessions

HideShow timer Statistics

\((n+k)^2 - 2nk =\)

A. \(n^2 + k^2\)
B. \(n^2\)
C. \(0\)
D. \(n^2 - k^2\)
E. \((n-k)^2\)

_________________
You've got what it takes, but it will take everything you've got
Senior Manager
Senior Manager
User avatar
P
Joined: 15 Feb 2018
Posts: 257
Premium Member
(n+k)^2 - 2nk =  [#permalink]

Show Tags

New post 30 Oct 2018, 00:43
\((n+k)^2\)
This is a 'square of a sum' quadratic. It follows this formula
\((n+k)^2\)=\(n^2+2nk+k^2\)

Inserting that back into the equation
\(n^2+2nk+k^2\)-2nk

=\(n^2+2nk-2nk+k^2\)

=\(n^2+k^2\)

A
CEO
CEO
User avatar
V
Joined: 12 Sep 2015
Posts: 3782
Location: Canada
Re: (n+k)^2 - 2nk =  [#permalink]

Show Tags

New post 21 Feb 2019, 13:44
Top Contributor
pushpitkc wrote:
\((n+k)^2 - 2nk =\)

A. \(n^2 + k^2\)
B. \(n^2\)
C. \(0\)
D. \(n^2 - k^2\)
E. \((n-k)^2\)


My approach would have been the same as that provided by philipssonicare

That said, we can also solve this problem by plugging in values and evaluating

Here's what I mean.

If n = 2 and k = 1, then:
(n + k)² - 2nk = (2 + 1)² - 2(2)(1)
= 3² - 4
= 9 - 4
= 5
So, when n = 2 and k = 1, (n + k)² - 2nk = 5

This means the answer choice that is EQUIVALENT to (n + k)² - 2nk must also equal 5 when n = 2 and k = 1

Let's check the answer choices...
A. n² + k² = 2² + 1² = 5 PERFECT - keep
B. n² = 2² = 4. No good. We need 5. ELIMINATE.
C. 0 No good. We need 5. ELIMINATE.
D. n² - k² = 2² - 1² = 3. No good. We need 5. ELIMINATE
E. (n - k)² = (2 - 1)² = 1. No good. We need 5. ELIMINATE

By the process of elimination, the correct answer is A

Cheers,
Brent
_________________
Test confidently with gmatprepnow.com
Image
GMAT Club Bot
Re: (n+k)^2 - 2nk =   [#permalink] 21 Feb 2019, 13:44
Display posts from previous: Sort by

(n+k)^2 - 2nk =

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


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