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.
Thank you for using the timer!
We noticed you are actually not timing your practice. Click the START button first next time you use the timer.
There are many benefits to timing your practice, including:
Does GMAT RC seem like an uphill battle? e-GMAT is conducting a free webinar to help you learn reading strategies that can enable you to solve 700+ level RC questions with at least 90% accuracy in less than 10 days. Sat., Oct 19th at 7 am PDT
Re: If xy = 7 and x – y = 7, then x² +
[#permalink]
Show Tags
22 Mar 2017, 14:43
3
Top Contributor
2
GMATPrepNow wrote:
If xy = 7 and x – y = 7, then x² + y² =
(A) 35 (B) 42 (C) 49 (D) 56 (E) 63
The important thing to recognize here is that if we square (x - y), we get a x² term and a y² term. We also get an extra xy term, but that's okay, because we're given some information about the product xy.
So, take: x – y = 7 and... Square both sides: (x - y)² = 7² Expand: x² - 2xy + y² = 49 Since we're told xy = 7, we'll replace xy with 7 to get: x² - 2(7) + y² = 49 Simplify: x² - 14 + y² = 49 Add 14 to both sides: x² + y² = 63
“The heights by great men reached and kept were not attained in sudden flight but, they while their companions slept, they were toiling upwards in the night.” ―Henry Wadsworth Longfellow
Re: If xy = 7 and x – y = 7, then x² +
[#permalink]
Show Tags
16 Jul 2017, 13:09
If xy = 7 and x – y = 7, then x² + y² =
\((x - y)^2 = x^2 - 2xy + y^2\)
\(x^2 + y^2 = (x - y)^2 + 2xy\)
\(x^2 + y^2 = (7)^2 + 2 * 7\)
\(x^2 + y^2 = 49 + 14\)
\(x^2 + y^2 = 63\)
Hence, Answer is E
Did you like the answer? 1 Kudos Please _________________
"Nothing in this world can take the place of persistence. Talent will not: nothing is more common than unsuccessful men with talent. Genius will not; unrewarded genius is almost a proverb. Education will not: the world is full of educated derelicts. Persistence and determination alone are omnipotent."
Best AWA Template: https://gmatclub.com/forum/how-to-get-6-0-awa-my-guide-64327.html#p470475
Re: If xy = 7 and x – y = 7, then x² +
[#permalink]
Show Tags
19 Sep 2019, 07:16
Hello from the GMAT Club BumpBot!
Thanks to another GMAT Club member, I have just discovered this valuable topic, yet it had no discussion for over a year. I am now bumping it up - doing my job. I think you may find it valuable (esp those replies with Kudos).
Want to see all other topics I dig out? Follow me (click follow button on profile). You will receive a summary of all topics I bump in your profile area as well as via email.
_________________