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.
Nov 2007:30 AM PST
-08:30 AM PST
Learn what truly sets the UC Riverside MBA apart and how it helps in your professional growth
Nov 2211:00 AM IST
-01:00 PM IST
Do RC/MSR passages scare you? e-GMAT is conducting a masterclass to help you learn – Learn effective reading strategies Tackle difficult RC & MSR with confidence Excel in timed test environment- Nov 23
11:00 AM IST
-01:00 PM IST
Attend this free GMAT Algebra Webinar and learn how to master the most challenging Inequalities and Absolute Value problems with ease. 
Nov 2510:00 AM EST
-11:00 AM EST
Prefer video-based learning? The Target Test Prep OnDemand course is a one-of-a-kind video masterclass featuring 400 hours of lecture-style teaching by Scott Woodbury-Stewart, founder of Target Test Prep and one of the most accomplished GMAT instructors.
31 Jan 2016, 07:38
Kudos
Bookmarks
B
Be sure to select an answer first to save it in the Error Log before revealing the correct answer (OA)!
Difficulty:
65%
(hard)
Question Stats:
38% (01:55) correct
63%
(01:43)
wrong
based on 16
sessions
History
Date
Time
Result
Not Attempted Yet
What is the value of x^3 − 2x^2 + 7?
(1) 3x^3 − x = 2
(2) x^5 = 1
(1) 3x^3 − x = 2
(2) x^5 = 1
Archived Topic
Hi there,
This topic has been closed and archived due to inactivity or violation of community quality standards. No more replies are possible here.
Where to now? Join ongoing discussions on thousands of quality questions in our Data Sufficiency (DS) Forum
Still interested in this question? Check out the "Best Topics" block below for a better discussion on this exact question, as well as several more related questions.
Thank you for understanding, and happy exploring!
01 Feb 2016, 05:37
Kudos
Bookmarks
Forget conventional ways of solving math questions. In DS, Variable approach is the easiest and quickest way to find the answer without actually solving the problem. Remember equal number of variables and independent equations ensures a solution.
What is the value of x^3 − 2x^2 + 7?
(1) 3x^3 − x = 2
(2) x^5 = 1
In the original condition, there is 1 variable(x), which should match with the number of equations. So you need 1 equation. For 1) 1 equation, for 2) 1 equation, which is likely to make D the answer.
For 1), 3x^3-x-2=0, (x-1)(3x^2+3x+2)=0 and 3x^2+3x+2>0 is always valid(discriminant=3^2-4*3*2<0). Thus, x=1 and the answer is unique and sufficient.
For 2), x=1, which is unique and sufficient.
Therefore, the answer is D.
-> For cases where we need 1 more equation, such as original conditions with “1 variable”, or “2 variables and 1 equation”, or “3 variables and 2 equations”, we have 1 equation each in both 1) and 2). Therefore, there is 59 % chance that D is the answer, while A or B has 38% chance and C or E has 3% chance. Since D is most likely to be the answer using 1) and 2) separately according to DS definition. Obviously there may be cases where the answer is A, B, C or E.
What is the value of x^3 − 2x^2 + 7?
(1) 3x^3 − x = 2
(2) x^5 = 1
In the original condition, there is 1 variable(x), which should match with the number of equations. So you need 1 equation. For 1) 1 equation, for 2) 1 equation, which is likely to make D the answer.
For 1), 3x^3-x-2=0, (x-1)(3x^2+3x+2)=0 and 3x^2+3x+2>0 is always valid(discriminant=3^2-4*3*2<0). Thus, x=1 and the answer is unique and sufficient.
For 2), x=1, which is unique and sufficient.
Therefore, the answer is D.
-> For cases where we need 1 more equation, such as original conditions with “1 variable”, or “2 variables and 1 equation”, or “3 variables and 2 equations”, we have 1 equation each in both 1) and 2). Therefore, there is 59 % chance that D is the answer, while A or B has 38% chance and C or E has 3% chance. Since D is most likely to be the answer using 1) and 2) separately according to DS definition. Obviously there may be cases where the answer is A, B, C or E.
13 Feb 2016, 04:17
Kudos
Bookmarks
What is the value of x^3 − 2x^2 + 7?
(1) 3x^3 − x = 2
(2) x^5 = 1
Statement 1 : 3x^3 − x = 2
on simplifying this, we get (x-1)(3x^2+3x+2)=0 which gives either x=1 or some negative fractional value of x
if we put both values in given equation, we will get two different values, i.e., one is an integer and one is fraction => insuff
Statement 2 : x^5=1
this gives x=1 => sufficient
hence, answer is B.
PS : we can't assume ANYTHING in GMAT DS. That's the catch in statement 1.
(1) 3x^3 − x = 2
(2) x^5 = 1
Statement 1 : 3x^3 − x = 2
on simplifying this, we get (x-1)(3x^2+3x+2)=0 which gives either x=1 or some negative fractional value of x
if we put both values in given equation, we will get two different values, i.e., one is an integer and one is fraction => insuff
Statement 2 : x^5=1
this gives x=1 => sufficient
hence, answer is B.
PS : we can't assume ANYTHING in GMAT DS. That's the catch in statement 1.
