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Problem set question from Manhattan 12th - newby question

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Problem set question from Manhattan 12th - newby question [#permalink] New post 31 May 2012, 05:51
I've encounter a problem in GMAT Manhattan which I don't get.
This is a quadratic equation.
Given that d/4 + 8/d + 3 = 0 , what is d?

In the solution they say you multiply the entire equation with 4d and thus come up with d^2 + 32 + 12d. But how? I can find how especially d4 can become d^2 by doing that.

Would like to know a solution step by step.

Last edited by jonatande on 31 May 2012, 06:09, edited 1 time in total.
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Re: Problem set question from Manahttan - newby question [#permalink] New post 31 May 2012, 06:02
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jonatande wrote:
I've encounter a problem in GMAT Manhattan which I don't get.
This is a quadratic equation.
Given that d/4 + 8/d + 3 = 0 , what is d?

In the solution they say you multiply the entire equation with 4d and thus come up with d^2 + 32 + 12d. But how? I can find how especially d4 can become d^2 by doing that.

Would like to know a solution step by step.


If you multiply \frac{d}{4} + \frac{8}{d} + 3 = 0 by 4d you'll get: \frac{d}{4}*4d + \frac{8}{d}*4d + 3*4d = 0*4d --> d^2+32+12d=0 --> d=-8 or d=-4.

Hope it's clear.
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Quadratic Equation Doubt [#permalink] New post 23 Jun 2013, 05:56
In MGMAT Algebra, Quadratic Eqn, Problem Set - Page 62, Qn 2

Given that D/4 + 8/D + 3 = 0

What is D?

In solution he has multiplied 4d and got d^2+ 32 + 12 d .. How come 32?

by taking LCM as 4D, Wont the Numerator become 4 D^2 + 32 D + 12 D or D^2 + 8D + 3D ??

[Reveal] Spoiler:
OA : D = -8 / -4
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Re: Quadratic Equation Doubt [#permalink] New post 23 Jun 2013, 06:01
Expert's post
daisyhill1 wrote:
In MGMAT Algebra, Quadratic Eqn, Problem Set - Page 62, Qn 2

Given that D/4 + 8/D + 3 = 0

What is D?

In solution he has multiplied 4d and got d^2+ 32 + 12 d .. How come 32?

by taking LCM as 4D, Wont the Numerator become 4 D^2 + 32 D + 12 D or D^2 + 8D + 3D ??

[Reveal] Spoiler:
OA : D = -8 / -4


Merging topics. Please refer to the post above.

Hope it helps.
_________________

NEW TO MATH FORUM? PLEASE READ THIS: ALL YOU NEED FOR QUANT!!!

PLEASE READ AND FOLLOW: 11 Rules for Posting!!!

RESOURCES: [GMAT MATH BOOK]; 1. Triangles; 2. Polygons; 3. Coordinate Geometry; 4. Factorials; 5. Circles; 6. Number Theory; 7. Remainders; 8. Overlapping Sets; 9. PDF of Math Book; 10. Remainders; 11. GMAT Prep Software Analysis NEW!!!; 12. SEVEN SAMURAI OF 2012 (BEST DISCUSSIONS) NEW!!!; 12. Tricky questions from previous years. NEW!!!;

COLLECTION OF QUESTIONS:
PS: 1. Tough and Tricky questions; 2. Hard questions; 3. Hard questions part 2; 4. Standard deviation; 5. Tough Problem Solving Questions With Solutions; 6. Probability and Combinations Questions With Solutions; 7 Tough and tricky exponents and roots questions; 8 12 Easy Pieces (or not?); 9 Bakers' Dozen; 10 Algebra set. ,11 Mixed Questions, 12 Fresh Meat

DS: 1. DS tough questions; 2. DS tough questions part 2; 3. DS tough questions part 3; 4. DS Standard deviation; 5. Inequalities; 6. 700+ GMAT Data Sufficiency Questions With Explanations; 7 Tough and tricky exponents and roots questions; 8 The Discreet Charm of the DS ; 9 Devil's Dozen!!!; 10 Number Properties set., 11 New DS set.


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Re: Quadratic Equation Doubt   [#permalink] 23 Jun 2013, 06:01
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