Problem set question from Manhattan 12th - newby question : GMAT Quantitative Section
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Problem set question from Manhattan 12th - newby question

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Joined: 19 May 2012
Posts: 28
GMAT Date: 01-07-2013
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Problem set question from Manhattan 12th - newby question [#permalink]

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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]

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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]

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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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Posts: 35932
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Kudos [?]: 90101 [0], given: 10413

Re: Quadratic Equation Doubt [#permalink]

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