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.
Apr 2610:00 AM EDT
-11:00 AM EDT
The Target Test Prep course represents a quantum leap forward in GMAT preparation, a radical reinterpretation of the way that students should study. Try before you buy with a 5-day, full-access trial of the course for FREE!
Apr 2711:00 AM EDT
-12:00 PM EDT
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
Apr 2808:00 AM PDT
-11:00 AM PDT
Whether you are just beginning your MBA journey or fine-tuning your path to a 700+ score, GMAT Day is designed to give you a competitive edge.
22 Apr 2022, 03:15
Kudos
Bookmarks
C
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:
64% (02:51) correct
36%
(02:53)
wrong
based on 188
sessions
History
Date
Time
Result
Not Attempted Yet
If \(x + 1 = x^2\) and \(x > 0\), then \(2x^4\) is:
A. \(6 + 4√5\)
B. \(3 + 5√5\)
C. \(7 + 3√5\)
D. \(5 + 3√5\)
E. \(4 + 3√5\)
Are You Up For the Challenge: 700 Level Questions
A. \(6 + 4√5\)
B. \(3 + 5√5\)
C. \(7 + 3√5\)
D. \(5 + 3√5\)
E. \(4 + 3√5\)
Are You Up For the Challenge: 700 Level Questions
24 Apr 2022, 18:05
Kudos
Bookmarks
Solving \(x^2-x-1=0\) the positive root is \(x=\frac{1+\sqrt{5}}{2}\)
Playing a little with the expression:
\(x^2=x+1\)
\(x^4=(x+1)^2=x^2+2x+1=x+1+2x+1=3x+2\)
\(2x^4=6x+4\)
Substituting:
\(6*\frac{1+\sqrt{5}}{2}+4=3+3\sqrt{5}+4=7+3\sqrt{5}\)
IMO C
Playing a little with the expression:
\(x^2=x+1\)
\(x^4=(x+1)^2=x^2+2x+1=x+1+2x+1=3x+2\)
\(2x^4=6x+4\)
Substituting:
\(6*\frac{1+\sqrt{5}}{2}+4=3+3\sqrt{5}+4=7+3\sqrt{5}\)
IMO C
General Discussion
24 Apr 2022, 05:40
Kudos
Bookmarks
Bunuel
\(x^2-x-1=0…….x^2-x+(\frac{1}{2})^2-(\frac{1}{2})^2-1=0….(x-\frac{1}{2})^2-\frac{5}{4}=0\)
\((x-\frac{1}{2}-\frac{\sqrt{5}}{2}) (x-\frac{1}{2}+\frac{\sqrt{5}}{2})=0\)
As x>0, \(x=\frac{1}{2}+\frac{\sqrt{5}}{2} =\frac{1+\sqrt{5}}{2}\)
Thus, \(x^2=\frac{(1+5+2\sqrt{5})}{4}=\frac{3+\sqrt{5}}{2}\)
=> \(x^4=\frac{(9+5+6\sqrt{5})}{4}=\frac{7+3\sqrt{5}}{2}\)
And, \(2x^4=2*\frac{7+3\sqrt{5}}{2}=7+3\sqrt{5}\)
