BREAKING: Target Test Prep releases Brand New 2026 On Demand GMAT prep course

Redeem
TTP OnDemand GMAT Video Course
Featured Course

Target Test Prep GMAT OnDemand

Scott Woodbury-Stewart’s private virtual classroom — 400 hours of master-class video lessons for the GMAT Focus Edition.

  • 715+ score guarantee — highest in the industry (99th percentile)
  • 52 chapters · 1,500+ lessons · 4,000+ practice questions
  • 400 hours of video · 1,500+ instructor-led HD smartboard lessons
  • 300,000+ students accepted to Harvard, Stanford, Wharton, Booth & Sloan & more
  • 24/7 live support + weekly Zoom office hours with GMAT instructors
  • TTP AI Assist — 24/7 AI-powered virtual tutor for instant help
  • 1,200+ flashcards + AI-powered study assistant & daily calendar
  • OnDemand, LiveTeach & GMAT Bootcamp formats available
  • Also: GRE, SAT Math & Executive Assessment courses
  • MBA Admissions Consulting now available
  • 🏆 2025 EdTech Breakthrough Award: Test Prep Solution Provider of the Year
  • 200,000+ students served
  • 5-day free trial — $0 to start, no auto-billing, cancel anytime
★★★★★ 5.0 (559 reviews)
130-pt guarantee
$0 to start then $127/mo
Start Free 5-Day Trial Read 559 Reviews →

Finding the highest factor by Differentiation method

Expert replies
Post new topic Post Reply
Previous Topic Next Topic
Senior | Next Rank: 100 Posts
Posts: 57
Joined: Sun Jul 06, 2008 10:52 am
Thanked: 1 times
GMAT Score:640
by iikarthik » Tue Jul 27, 2010 11:51 am
Hi All,

I remember having read the use of differentiation to find the highest value of a given quadraric equation.

But am not able to get it right.
can someone pls explain what went wrong.

the equation is x^2-6x-27=0
by Diff with respect to X, we get 2x-6=0.hence x=3

but by factorising, we get the values of X as 9,-3.

Thanks
karthik
Top
Join the discussion
Log in to postLogin with Googleuse password
QUOTE IN REPLY
Source: — Problem Solving |

GMAT/MBA Expert

User avatar
GMAT Instructor
Posts: 16207
Joined: Mon Dec 08, 2008 6:26 pmFollowed by: 1268 members
Location: Vancouver, BC
Thanked: 5254 times
GMAT Score:770

by Brent@GMATPrepNow » Tue Jul 27, 2010 12:16 pm
Hi Karthik,

You are answering 2 different questions.

You would use differentiation to find the maximum or minimum value of an expresson such as x^2-6x-27
However, if you wish to solve the equation x^2-6x-27 = 0, then you would factor --> (x-9)(x+3)=0 --> x=9, -3

Cheers,
Brent

PS: Differentiation is not required on the GMAT :-)
PPS: the expression x^2-6x-27 has no maximum value, but its minimum value occurs at x=3


iikarthik wrote:Hi All,

I remember having read the use of differentiation to find the highest value of a given quadraric equation.

But am not able to get it right.
can someone pls explain what went wrong.

the equation is x^2-6x-27=0
by Diff with respect to X, we get 2x-6=0.hence x=3

but by factorising, we get the values of X as 9,-3.

Thanks
karthik
Brent Hanneson - Creator of GMATPrepNow.com
Image
Top
Join the discussion
Log in to postLogin with Googleuse password
QUOTE IN REPLY
Legendary Member
Posts: 2326
Joined: Mon Jul 28, 2008 3:54 amFollowed by: 2 members
Thanked: 173 times
GMAT Score:710

by gmatmachoman » Wed Jul 28, 2010 2:54 am
Brent Hanneson wrote:Hi Karthik,

You are answering 2 different questions.

You would use differentiation to find the maximum or minimum value of an expresson such as x^2-6x-27
However, if you wish to solve the equation x^2-6x-27 = 0, then you would factor --> (x-9)(x+3)=0 --> x=9, -3

Cheers,
Brent

PS: Differentiation is not required on the GMAT :-)
PPS: the expression x^2-6x-27 has no maximum value, but its minimum value occurs at x=3


iikarthik wrote:Hi All,

I remember having read the use of differentiation to find the highest value of a given quadraric equation.

But am not able to get it right.
can someone pls explain what went wrong.

the equation is x^2-6x-27=0
by Diff with respect to X, we get 2x-6=0.hence x=3

but by factorising, we get the values of X as 9,-3.

Thanks
karthik
D = b^2 -4ac
= 6^2 -4 *1*(-27)
>0
Minimum value when D >0 and Maximum value when D<0

So for the above expression only Minimum can be found out as D is >0

Hope I am correct..
Top
Join the discussion
Log in to postLogin with Googleuse password
QUOTE IN REPLY
Post new topic Post Reply
• Page 1 of 1