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

 It is currently 20 Oct 2019, 07:49

### 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 x^2=2x+1, x^3=？

Author Message
TAGS:

### Hide Tags

Math Revolution GMAT Instructor
Joined: 16 Aug 2015
Posts: 8017
GMAT 1: 760 Q51 V42
GPA: 3.82

### Show Tags

01 Mar 2017, 04:54
00:00

Difficulty:

65% (hard)

Question Stats:

58% (02:04) correct 42% (02:33) wrong based on 119 sessions

### HideShow timer Statistics

If $$x^2=2x+1, x^3$$=？

A. 4x
B. 5x+2
C. 5x-1
D. 3x+2
E. 3x-2

_________________
MathRevolution: Finish GMAT Quant Section with 10 minutes to spare
The one-and-only World’s First Variable Approach for DS and IVY Approach for PS with ease, speed and accuracy.
"Only $79 for 1 month Online Course" "Free Resources-30 day online access & Diagnostic Test" "Unlimited Access to over 120 free video lessons - try it yourself" ##### Most Helpful Community Reply Senior Manager Joined: 19 Apr 2016 Posts: 268 Location: India GMAT 1: 570 Q48 V22 GMAT 2: 640 Q49 V28 GPA: 3.5 WE: Web Development (Computer Software) Re: If x^2=2x+1, x^3=？ [#permalink] ### Show Tags 01 Mar 2017, 05:16 6 MathRevolution wrote: If $$x^2=2x+1, x^3$$=？ A. 4x B. 5x+2 C. 5x-1 D. 3x+2 E. 3x-2 $$x^2 = 2x+1$$ $$x^3 = (2x+1)*x$$ $$x^3 = 2*x^2 + x$$ $$x^3 = 2*(2x+1) + x$$ $$x^3 = 5x+1$$ Hence option B is correct Hit Kudos if you liked it ##### General Discussion Math Revolution GMAT Instructor Joined: 16 Aug 2015 Posts: 8017 GMAT 1: 760 Q51 V42 GPA: 3.82 Re: If x^2=2x+1, x^3=？ [#permalink] ### Show Tags 03 Mar 2017, 01:13 ==> $$x^3=x(x^2)=x(2x+1)=2x^2+x=2(2x+1)+x=5x+2$$ Answer: B _________________ MathRevolution: Finish GMAT Quant Section with 10 minutes to spare The one-and-only World’s First Variable Approach for DS and IVY Approach for PS with ease, speed and accuracy. "Only$79 for 1 month Online Course"
"Free Resources-30 day online access & Diagnostic Test"
"Unlimited Access to over 120 free video lessons - try it yourself"
Target Test Prep Representative
Status: Founder & CEO
Affiliations: Target Test Prep
Joined: 14 Oct 2015
Posts: 8109
Location: United States (CA)

### Show Tags

06 Mar 2017, 18:38
1
1
MathRevolution wrote:
If $$x^2=2x+1, x^3$$=？

A. 4x
B. 5x+2
C. 5x-1
D. 3x+2
E. 3x-2

Since we are given x^2 = 2x + 1 and need to determine the value of x^3, we can multiply both sides of our equation by x and we have:

x(x^2) = x(2x + 1)

x^3 = 2x^2 + x

We can substitute (2x + 1) for x^2 on the right hand side of the equation and obtain:

x^3 = 2(2x + 1) + x

x^3 = 4x + 2 + x

x^3 = 5x + 2

_________________

# 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.

Director
Joined: 09 Mar 2018
Posts: 994
Location: India

### Show Tags

18 Feb 2019, 01:30
MathRevolution wrote:
If $$x^2=2x+1, x^3$$=？

A. 4x
B. 5x+2
C. 5x-1
D. 3x+2
E. 3x-2

Lazy is the keyword

Multiply if statement by x

x^2 = 2x + 1

$$x^3 = 2x^2 + 1$$

Substitute for x^2 again
2(2x+1) + x
4x + 2 +x
we get 5x +2
_________________
If you notice any discrepancy in my reasoning, please let me know. Lets improve together.

Quote which i can relate to.
Many of life's failures happen with people who do not realize how close they were to success when they gave up.
Re: If x^2=2x+1, x^3=？   [#permalink] 18 Feb 2019, 01:30
Display posts from previous: Sort by