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

 It is currently 20 Aug 2019, 20:18

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

If ab = 5 and (a - b)^2 = 19, what is the value of a^2 + b^2 ?

Author Message
TAGS:

Hide Tags

Math Expert
Joined: 02 Sep 2009
Posts: 57155
If ab = 5 and (a - b)^2 = 19, what is the value of a^2 + b^2 ?  [#permalink]

Show Tags

31 Jul 2019, 23:49
00:00

Difficulty:

15% (low)

Question Stats:

92% (00:49) correct 8% (01:40) wrong based on 26 sessions

HideShow timer Statistics

If ab = 5 and (a - b)^2 = 19, what is the value of a^2 + b^2 ?

A. 14
B. 18
C. 24
D. 25
E. 29

_________________
Intern
Joined: 04 Jun 2018
Posts: 1
Re: If ab = 5 and (a - b)^2 = 19, what is the value of a^2 + b^2 ?  [#permalink]

Show Tags

01 Aug 2019, 00:49
First: We know that ab = 5
So: (a-b)^2 = (a-b)(a-b) = 19
a^2 -ab -ba + b^2 = 19
a^2 -2ab + b^2 = 19
a^2 -2(5) + b^2 = 19
a^2 -10 + b^2 = 19
a^2 + b^2 = 29.
Ans: 29 (E)
Target Test Prep Representative
Status: Founder & CEO
Affiliations: Target Test Prep
Joined: 14 Oct 2015
Posts: 7412
Location: United States (CA)
Re: If ab = 5 and (a - b)^2 = 19, what is the value of a^2 + b^2 ?  [#permalink]

Show Tags

06 Aug 2019, 17:42
Bunuel wrote:
If ab = 5 and (a - b)^2 = 19, what is the value of a^2 + b^2 ?

A. 14
B. 18
C. 24
D. 25
E. 29

(a - b)^2 = 19

a^2 - 2ab + b^2 = 19

Substituting 5 for ab, we have:

a^2 - 2(5) + b^2 = 19

a^2 - 10 + b^2 = 19

a^2 + b^2 = 29

_________________

Scott Woodbury-Stewart

Founder and CEO

Scott@TargetTestPrep.com
122 Reviews

5-star rated online GMAT quant
self study course

See why Target Test Prep is the top rated GMAT quant course on GMAT Club. Read Our Reviews

If you find one of my posts helpful, please take a moment to click on the "Kudos" button.

Re: If ab = 5 and (a - b)^2 = 19, what is the value of a^2 + b^2 ?   [#permalink] 06 Aug 2019, 17:42
Display posts from previous: Sort by