Welcome! Check out our free B-School Guides to learn how you compare with other applicants.

## help neeeded plsss!!!

This topic has 6 member replies
marmar29 Rising GMAT Star
Joined
15 Feb 2011
Posted:
61 messages
help neeeded plsss!!! Mon Mar 12, 2012 11:21 pm
Elapsed Time: 00:00
• Lap #[LAPCOUNT] ([LAPTIME])
pls help me in ths arrangemnt

arrange the following to solve 'd' interms of 'e'

3d - 7^2 / (4+5d) = e

plssssssssss i ve an exam after a while & need to see the steps
ASAP
thanks
marmar

Need free GMAT or MBA advice from an expert? Register for Beat The GMAT now and post your question in these forums!
Snowbirds Just gettin' started!
Joined
11 Mar 2012
Posted:
5 messages
Tue Mar 13, 2012 2:40 am
First thing to notice is that d=-4/5 cannot be a solution.

Then just solve....

12d+15d^2 - 49 = 4e+5de
15d^2 + (12-5e)d + (-4e-49) = 0

Notice this is now in quadratic form, now just solve however you prefer to solve quadratics. Someone else can write out the details if necessary.

I'm not an expert, but this does not seem like a gmat question...

sanju09 GMAT Instructor
Joined
21 Jan 2009
Posted:
3262 messages
Followed by:
48 members
Thanked:
190 times
GMAT Score:
760
Tue Mar 13, 2012 2:42 am
marmar29 wrote:
pls help me in ths arrangemnt

arrange the following to solve 'd' interms of 'e'

3d - 7^2 / (4+5d) = e

plssssssssss i ve an exam after a while & need to see the steps
ASAP
thanks
marmar
If the bracket use is correct, and the original question is how it appears here, then following steps can be followed:

3d - 7^2 / (4+5d) = e (multiply both sides with 4 + 5 d)

3d (4 + 5 d) - 49 = e (4 + 5 d) {open the brackets}

12 d - 15 d^2 - 49 = 4 e + 5 e d (take every term to one side of ‘=’ so as to make the coefficient of d^2 positive)

15 d^2 + 5 e d - 12 d + 4 e + 49 = 0

15 d^2 + (5 e - 12) d + (4 e + 49) = 0 {this is a quadratic equation in d, use quadratic formula to solve for d}

d = [- (5 e - 12) ± √ {(5 e - 12) ^2 - 4 X 15 X (4 e + 49)}]/ (2 X 15)

Solve further if you please, these are the two values of d in terms of e.

_________________
The laws of nature are but the mathematical thoughts of God. ~Euclid

Joined
29 Feb 2012
Posted:
2 messages
Tue Mar 13, 2012 7:31 am
The Quadratic equation seems dubious to me.

3d - 7^2 / (4+5d) = e (multiply both sides with 4 + 5 d)
3d (4 + 5 d) - 49 = e (4 + 5 d) {open the brackets}
Then:

12 d + 15 d^2 - 49 = 4 e + 5 e d
15 d^2 + 12 d - 5 e d - 49 - 4 e = 0
15 d^2 + d(12 - 5 e) - (49 + 4 e) = 0 {this is a quadratic equation in d, use quadratic formula to solve for d}

@Sanju09 : Am I wrong in identifying anything?

sanju09 GMAT Instructor
Joined
21 Jan 2009
Posted:
3262 messages
Followed by:
48 members
Thanked:
190 times
GMAT Score:
760
Wed Mar 14, 2012 1:42 am
The Quadratic equation seems dubious to me.

3d - 7^2 / (4+5d) = e (multiply both sides with 4 + 5 d)
3d (4 + 5 d) - 49 = e (4 + 5 d) {open the brackets}
Then:

12 d + 15 d^2 - 49 = 4 e + 5 e d
15 d^2 + 12 d - 5 e d - 49 - 4 e = 0
15 d^2 + d(12 - 5 e) - (49 + 4 e) = 0 {this is a quadratic equation in d, use quadratic formula to solve for d}

@Sanju09 : Am I wrong in identifying anything?
What did you identify in the first place?

_________________
The laws of nature are but the mathematical thoughts of God. ~Euclid

Joined
29 Feb 2012
Posted:
2 messages
Wed Mar 14, 2012 2:27 am
Considering the equation in the form:
A d^2 + B d + C = 0

My Equation:
15 d^2 + d(12 - 5 e) - (49 + 4 e) = 0
A = 15
B = (12 - 5 e)
C = - (49 + 4 e)

15 d^2 + (5 e - 12) d + (4 e + 49) = 0
A = 15
B = (5 e - 12)
C = (49 + 4 e)

Its just the values that we are getting different, I have no doubt or concern over the method you suggested.

Thanks,
Vikash

sanju09 GMAT Instructor
Joined
21 Jan 2009
Posted:
3262 messages
Followed by:
48 members
Thanked:
190 times
GMAT Score:
760
Wed Mar 14, 2012 2:51 am
Considering the equation in the form:
A d^2 + B d + C = 0

My Equation:
15 d^2 + d(12 - 5 e) - (49 + 4 e) = 0
A = 15
B = (12 - 5 e)
C = - (49 + 4 e)

15 d^2 + (5 e - 12) d + (4 e + 49) = 0
A = 15
B = (5 e - 12)
C = (49 + 4 e)

Its just the values that we are getting different, I have no doubt or concern over the method you suggested.

Thanks,
Vikash
Oh I got your point, my work should have continued as…

3d (4 + 5 d) - 49 = e (4 + 5 d) {open the brackets}

12 d + 15 d^2 - 49 = 4 e + 5 e d (take every term to one side of ‘=’ keeping the coefficient of d^2 positive)

15 d^2 = 5 e d + 12 d = 4 e = 49 = 0

15 d^2 = (5 e - 12) d = (4 e + 49) = 0 {this is a quadratic equation in d, use quadratic formula to solve for d}

d = [(5 e - 12) ± √ {(5 e - 12) ^2 + 4 X 15 X (4 e + 49)}]/ (2 X 15)

Solve further if you please, these are the two values of d in terms of e.

regards

_________________
The laws of nature are but the mathematical thoughts of God. ~Euclid

### Best Conversation Starters

1 varun289 38 topics
2 killerdrummer 22 topics
3 sana.noor 20 topics
4 sanaa.rizwan 14 topics
5 guerrero 14 topics
See More Top Beat The GMAT Members...

### Most Active Experts

1 Brent@GMATPrepNow

GMAT Prep Now Teacher

204 posts
2 GMATGuruNY

The Princeton Review Teacher

136 posts
3 Jim@StratusPrep

Stratus Prep

100 posts
4 Anju@Gurome

Gurome

74 posts