Events & Promotions
|
|
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
Track
Your Progress
Practice
Pays
Not interested in getting valuable practice questions and articles delivered to your email? No problem, unsubscribe here.
May 0111:00 AM PDT
-12:00 PM PDT
Free- full-length test + 15 concept videos + 150+ short videos + study plan!
May 0312:30 AM EDT
-01:30 AM EDT
Learn how Kamakshi achieved a GMAT 675 with an impressive 96th %ile in Data Insights. Discover the unique methods and exam strategies that helped her excel in DI along with other sections for a balanced and high score.
GMATbuster92
Joined: 28 Jun 2018
Last visit: 20 Jul 2019
Posts: 147
Given Kudos: 32
Location: India
Concentration: Finance, Marketing
Schools: CUHK '21 (II)
GMAT 1: 650 Q49 V30
GPA: 4
Products:
Updated on: 11 Sep 2018, 23:37
Originally posted by GMATbuster92 on 11 Sep 2018, 23:36.
Last edited by Bunuel on 11 Sep 2018, 23:37, edited 1 time in total.
Last edited by Bunuel on 11 Sep 2018, 23:37, edited 1 time in total.
Renamed the topic and edited the question.
Kudos
Bookmarks
D
Be sure to select an answer first to save it in the Error Log before revealing the correct answer (OA)!
Difficulty:
45%
(medium)
Question Stats:
57% (01:48) correct
43%
(01:53)
wrong
based on 82
sessions
History
Date
Time
Result
Not Attempted Yet
If integer k > 0 and x^2 − 7x + k = 0, what is the value of k?
(1) Both roots are prime number
(2) 2 is one of root of the equation
(1) Both roots are prime number
(2) 2 is one of root of the equation
11 Sep 2018, 23:43
Kudos
Bookmarks
If integer k > 0 and x^2 − 7x + k = 0, what is the value of k?
Viete's theorem states that for the roots \(x_1\) and \(x_2\) of a quadratic equation \(ax^2+bx+c=0\):
\(x_1+x_2=\frac{-b}{a}\) AND \(x_1*x_2=\frac{c}{a}\).
(1) Both roots are prime number.
According to the theorem: \(x_1+x_2=\frac{-b}{a}=7\). 7 can be expressed as the sum of two primes only in one way 2 + 5 = 7. Knowing the roots we can find the value of k. Sufficient.
(2) 2 is one of root of the equation. Plug x = 2: 2^2 − 7*2 + k = 0. We can find k. Sufficient.
Answer: D.
Hope it's clear.
Viete's theorem states that for the roots \(x_1\) and \(x_2\) of a quadratic equation \(ax^2+bx+c=0\):
\(x_1+x_2=\frac{-b}{a}\) AND \(x_1*x_2=\frac{c}{a}\).
(1) Both roots are prime number.
According to the theorem: \(x_1+x_2=\frac{-b}{a}=7\). 7 can be expressed as the sum of two primes only in one way 2 + 5 = 7. Knowing the roots we can find the value of k. Sufficient.
(2) 2 is one of root of the equation. Plug x = 2: 2^2 − 7*2 + k = 0. We can find k. Sufficient.
Answer: D.
Hope it's clear.
12 Sep 2018, 00:32
Kudos
Bookmarks
Bunuel
can you explain why the sum has been taken as 7 and not 5? (3+2)
